FastModel: refactor us_ticker code, make names intuitive

 - reanme US_TICKER_TIMER1 to US_TICKER_COUNTER
 - reanme US_TICKER_TIMER2 to US_TICKER_INTERRUPT

Author: Qinghao Shi

targets/TARGET_ARM_FM/TARGET_FVP_MPS2/us_ticker.c

@@ -16,24 +16,24 @@
 #include <stddef.h>
 #include "us_ticker_api.h"
 #include "PeripheralNames.h"
-#define US_TICKER_TIMER1      CMSDK_DUALTIMER1
-#define US_TICKER_TIMER2      CMSDK_DUALTIMER2
+#define US_TICKER_COUNTER     CMSDK_DUALTIMER1
+#define US_TICKER_INTERRUPT   CMSDK_DUALTIMER2
 #define US_TICKER_TIMER_IRQn  DUALTIMER_IRQn
 
 /** mbed OS HAL API defined us_ticker as an increment ticker
  *  MPS2 platform provided in SSE-200 are decrement tickers
  *  with interrupt fired counter reaches 0.
  *
  *  So 2 Timers are used to construct mbed OS HAL ticker.
- *  
+ *
  *  TIMER1 is for counting, and returns inverted binary when read from it
  *  TIMER1 will be kept in free-running mode (default, and not generate interrupts)
- *  
+ *
  *  TIMER2 is for generating interrupts
  *  So TIMER2 is set to periodic mode, which start decrement counting form LOADVALUE generates interrupts at 0
- *  and TIMER2 also set into one-shot mode, which counter halts when is reaches 0 
+ *  and TIMER2 also set into one-shot mode, which counter halts when is reaches 0
  */
- 
+
 static int us_ticker_inited = 0;
 
 void us_ticker_init(void)
@@ -43,47 +43,47 @@ void us_ticker_init(void)
         return;
     }
 
-    US_TICKER_TIMER1->TimerControl  = 0x0ul; // disable TIMER1 and reset all control
-    US_TICKER_TIMER2->TimerControl  = 0x0ul; // disable TIMER2 and reset all control
+    US_TICKER_COUNTER->TimerControl    = 0x0ul; // disable TIMER1 and reset all control
+    US_TICKER_INTERRUPT->TimerControl  = 0x0ul; // disable TIMER2 and reset all control
 
-    US_TICKER_TIMER1->TimerLoad     = 0xFFFFFFFFul;
-    US_TICKER_TIMER2->TimerLoad     = 0xFFFFFFFFul;
+    US_TICKER_COUNTER->TimerLoad       = 0xFFFFFFFFul;
+    US_TICKER_INTERRUPT->TimerLoad     = 0xFFFFFFFFul;
 
-    US_TICKER_TIMER1->TimerControl |= CMSDK_DUALTIMER1_CTRL_SIZE_Msk; // set TIMER1 to 32 bit counter
-    US_TICKER_TIMER2->TimerControl |= CMSDK_DUALTIMER2_CTRL_SIZE_Msk; // set TIMER2 to 32 bit counter
+    US_TICKER_COUNTER->TimerControl   |= CMSDK_DUALTIMER1_CTRL_SIZE_Msk; // set TIMER1 to 32 bit counter
+    US_TICKER_INTERRUPT->TimerControl |= CMSDK_DUALTIMER2_CTRL_SIZE_Msk; // set TIMER2 to 32 bit counter
 
-    US_TICKER_TIMER1->TimerControl |= 0x1 << CMSDK_DUALTIMER1_CTRL_PRESCALE_Pos; // set TIMER1 with 4 stages prescale
-    US_TICKER_TIMER2->TimerControl |= 0x1 << CMSDK_DUALTIMER2_CTRL_PRESCALE_Pos; // set TIMER2 with 4 stages prescale
+    US_TICKER_COUNTER->TimerControl   |= 0x1 << CMSDK_DUALTIMER1_CTRL_PRESCALE_Pos; // set TIMER1 with 4 stages prescale
+    US_TICKER_INTERRUPT->TimerControl |= 0x1 << CMSDK_DUALTIMER2_CTRL_PRESCALE_Pos; // set TIMER2 with 4 stages prescale
 
-    US_TICKER_TIMER2->TimerControl |= CMSDK_DUALTIMER2_CTRL_MODE_Msk;     // set TIMER2 periodic mode
-    US_TICKER_TIMER2->TimerControl |= CMSDK_DUALTIMER2_CTRL_ONESHOOT_Msk; // set TIMER2 one-shot mode
+    US_TICKER_INTERRUPT->TimerControl |= CMSDK_DUALTIMER2_CTRL_MODE_Msk;     // set TIMER2 periodic mode
+    US_TICKER_INTERRUPT->TimerControl |= CMSDK_DUALTIMER2_CTRL_ONESHOOT_Msk; // set TIMER2 one-shot mode
 
-    US_TICKER_TIMER1->TimerControl |= CMSDK_DUALTIMER1_CTRL_EN_Msk; // enable TIMER1 counter
+    US_TICKER_COUNTER->TimerControl |= CMSDK_DUALTIMER1_CTRL_EN_Msk; // enable TIMER1 counter
 
     NVIC_SetVector(US_TICKER_TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
     us_ticker_inited = 1;
 }
 
 void us_ticker_free(void)
 {
-    US_TICKER_TIMER1->TimerControl  &= ~CMSDK_DUALTIMER1_CTRL_EN_Msk; // disable TIMER1
-    US_TICKER_TIMER2->TimerControl  &= ~CMSDK_DUALTIMER2_CTRL_EN_Msk; // disable TIMER2
+    US_TICKER_COUNTER->TimerControl    &= ~CMSDK_DUALTIMER1_CTRL_EN_Msk; // disable TIMER1
+    US_TICKER_INTERRUPT->TimerControl  &= ~CMSDK_DUALTIMER2_CTRL_EN_Msk; // disable TIMER2
     us_ticker_disable_interrupt();
     us_ticker_inited = 0;
 }
 
 uint32_t us_ticker_read()
 {
-    return ~US_TICKER_TIMER1->TimerValue;
+    return ~US_TICKER_COUNTER->TimerValue;
 }
 
 void us_ticker_set_interrupt(timestamp_t timestamp)
 {
     uint32_t delta =  timestamp - us_ticker_read();
-    US_TICKER_TIMER2->TimerControl &= ~CMSDK_DUALTIMER2_CTRL_EN_Msk;   // disable TIMER2
-    US_TICKER_TIMER2->TimerLoad = delta;                               // Set TIMER2 load value
-    US_TICKER_TIMER2->TimerControl |= CMSDK_DUALTIMER2_CTRL_INTEN_Msk; // enable TIMER2 interrupt
-    US_TICKER_TIMER2->TimerControl |= CMSDK_DUALTIMER2_CTRL_EN_Msk;    // enable TIMER2 counter
+    US_TICKER_INTERRUPT->TimerControl &= ~CMSDK_DUALTIMER2_CTRL_EN_Msk;   // disable TIMER2
+    US_TICKER_INTERRUPT->TimerLoad = delta;                               // Set TIMER2 load value
+    US_TICKER_INTERRUPT->TimerControl |= CMSDK_DUALTIMER2_CTRL_INTEN_Msk; // enable TIMER2 interrupt
+    US_TICKER_INTERRUPT->TimerControl |= CMSDK_DUALTIMER2_CTRL_EN_Msk;    // enable TIMER2 counter
     NVIC_EnableIRQ(US_TICKER_TIMER_IRQn);
 }
 
@@ -96,14 +96,14 @@ void us_ticker_fire_interrupt(void)
 
 void us_ticker_disable_interrupt(void)
 {
-    US_TICKER_TIMER2->TimerControl &= ~CMSDK_DUALTIMER2_CTRL_INTEN_Msk;
-    US_TICKER_TIMER2->TimerControl &= ~CMSDK_DUALTIMER2_CTRL_EN_Msk;  // disable TIMER2
+    US_TICKER_INTERRUPT->TimerControl &= ~CMSDK_DUALTIMER2_CTRL_INTEN_Msk;
+    US_TICKER_INTERRUPT->TimerControl &= ~CMSDK_DUALTIMER2_CTRL_EN_Msk;  // disable TIMER2
     NVIC_DisableIRQ(US_TICKER_TIMER_IRQn);
 }
 
 void us_ticker_clear_interrupt(void)
 {
-    US_TICKER_TIMER2->TimerIntClr = CMSDK_DUALTIMER2_INTCLR_Msk;
+    US_TICKER_INTERRUPT->TimerIntClr = CMSDK_DUALTIMER2_INTCLR_Msk;
 }
 
 const ticker_info_t *us_ticker_get_info(void)