[STM32] remove superfluous calls to SystemCoreClockUpdate

Supported toolchains initialization steps have been modified to make sure
that mbed_sdk_initi is called _after_ RAM initialization and _before_ C++
objects creation.

since this was done, there is no need to redundant SystemCoreClockUpdates
in the drivers

Author: Laurent MEUNIER

targets/TARGET_STM/TARGET_STM32F0/pwmout_api.c

@@ -162,9 +162,6 @@ void pwmout_period_us(pwmout_t* obj, int us) {
 
     __HAL_TIM_DISABLE(&TimHandle);
 
-    // Update the SystemCoreClock variable
-    SystemCoreClockUpdate();
-
     /* To make it simple, we use to possible prescaler values which lead to:
      * pwm unit = 1us, period/pulse can be from 1us to 65535us
      * or

targets/TARGET_STM/TARGET_STM32F0/serial_api.c

@@ -90,10 +90,6 @@ static void init_uart(serial_t *obj)
         huart->Init.Mode = UART_MODE_TX_RX;
     }
 
-    /* uAMR & ARM: Call to UART init is done between reset of pre-initialized variables */
-	  /* and before HAL Init. SystemCoreClock init required here */
-    SystemCoreClockUpdate();
-
     if (HAL_UART_Init(huart) != HAL_OK) {
         error("Cannot initialize UART\n");
     }

targets/TARGET_STM/TARGET_STM32F1/pwmout_api.c

@@ -152,9 +152,6 @@ void pwmout_period_us(pwmout_t* obj, int us)
 
     __HAL_TIM_DISABLE(&TimHandle);
 
-    // Update the SystemCoreClock variable
-    SystemCoreClockUpdate();
-
     /* To make it simple, we use to possible prescaler values which lead to:
      * pwm unit = 1us, period/pulse can be from 1us to 65535us
      * or

targets/TARGET_STM/TARGET_STM32F1/serial_api.c

@@ -82,10 +82,6 @@ static void init_uart(serial_t *obj)
         huart->Init.Mode = UART_MODE_TX_RX;
     }
 
-    /* uAMR & ARM: Call to UART init is done between reset of pre-initialized variables */
-    /* and before HAL Init. SystemCoreClock init required here */
-    SystemCoreClockUpdate();
-
     if (HAL_UART_Init(huart) != HAL_OK) {
         error("Cannot initialize UART\n");
     }

targets/TARGET_STM/TARGET_STM32F2/serial_api.c

@@ -82,10 +82,6 @@ static void init_uart(serial_t *obj)
         huart->Init.Mode = UART_MODE_TX_RX;
     }
 
-    /* uAMR & ARM: Call to UART init is done between reset of pre-initialized variables */
-    /* and before HAL Init. SystemCoreClock init required here */
-    SystemCoreClockUpdate();
-
     if (HAL_UART_Init(huart) != HAL_OK) {
         error("Cannot initialize UART\n");
     }

targets/TARGET_STM/TARGET_STM32F3/i2c_api.c

@@ -113,9 +113,6 @@ void i2c_frequency(i2c_t *obj, int hz)
     timeout = LONG_TIMEOUT;
     while ((__HAL_I2C_GET_FLAG(&I2cHandle, I2C_FLAG_BUSY)) && (timeout-- != 0));
 
-    // Update the SystemCoreClock variable.
-    SystemCoreClockUpdate();
-
     /*
        Values calculated with I2C_Timing_Configuration_V1.0.1.xls file (see AN4235)
        * Standard mode (up to 100 kHz)

targets/TARGET_STM/TARGET_STM32F3/serial_api.c

@@ -82,9 +82,6 @@ static void init_uart(serial_t *obj)
         huart->Init.Mode = UART_MODE_TX_RX;
     }
 
-    /* uAMR & ARM: Call to UART init is done between reset of pre-initialized variables */
-    /* and before HAL Init. SystemCoreClock init required here */
-    SystemCoreClockUpdate();
 
     if (HAL_UART_Init(huart) != HAL_OK) {
         error("Cannot initialize UART\n");

targets/TARGET_STM/TARGET_STM32F4/serial_api.c

@@ -84,10 +84,6 @@ static void init_uart(serial_t *obj)
         huart->Init.Mode = UART_MODE_TX_RX;
     }
 
-    /* uAMR & ARM: Call to UART init is done between reset of pre-initialized variables */
-	  /* and before HAL Init. SystemCoreClock init required here */
-    SystemCoreClockUpdate();
-
     if (HAL_UART_Init(huart) != HAL_OK) {
         error("Cannot initialize UART\n");
     }

targets/TARGET_STM/TARGET_STM32F7/serial_api.c

@@ -83,10 +83,6 @@ static void init_uart(serial_t *obj)
         huart->Init.Mode = UART_MODE_TX_RX;
     }
 
-    /* uAMR & ARM: Call to UART init is done between reset of pre-initialized variables */
-    /* and before HAL Init. SystemCoreClock init required here */
-    SystemCoreClockUpdate();
-
     if (HAL_UART_Init(huart) != HAL_OK) {
         error("Cannot initialize UART\n");
     }

targets/TARGET_STM/TARGET_STM32L1/pwmout_api.c

@@ -166,8 +166,6 @@ void pwmout_period_us(pwmout_t* obj, int us)
 
     __HAL_TIM_DISABLE(&TimHandle);
 
-    SystemCoreClockUpdate();
-
     /* To make it simple, we use to possible prescaler values which lead to:
      * pwm unit = 1us, period/pulse can be from 1us to 65535us
      * or