Move trng code from target_nrf5 to target_nrf5x

After rebase, the build target NRF52840_DK is using TARGET_NRF5x,
instead of TARGET_NRF5. Moved Cryptocell TRNG related code from
`targets/TARGET_NORDIC/TARGET_NRF5/` to `targets/TARGET_NORDIC/TARGET_NRF5x/`

Author: Ron Eldor

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF51/objects.h

@@ -47,13 +47,6 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
-#if DEVICE_CRYPTOCELL
-#include "objects_cryptocell.h"
-#else
-struct trng_s {
-    uint32_t placeholder;
-};
-#endif
 
 struct serial_s {
     uint32_t placeholder; // struct is unused by nRF5x API implementation
@@ -92,6 +85,10 @@ struct flash_s {
     uint32_t placeholder;
 };
 
+struct trng_s {
+    uint32_t placeholder;
+};
+
 #include "gpio_object.h"
 
 #ifdef __cplusplus

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF51/trng_api.c

@@ -41,7 +41,6 @@
 #include "hal/trng_api.h"
 #include "hal/lp_ticker_api.h"
 
-#if !defined(DEVICE_CRYPTOCELL)
 #include "nrf_drv_rng.h"
 
 #define DEFAULT_TIMEOUT_US (1000*1000)
@@ -180,5 +179,4 @@ int trng_get_bytes(trng_t *obj, uint8_t *output, size_t length, size_t *output_l
     return (*output_length == 0) ? -1 : 0;
 }
 
-#endif/* !DEVICE_CRYPTOCELL */
 #endif

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/objects.h

@@ -54,6 +54,14 @@ extern "C" {
 
 #include "nrf_uart.h"
 
+#if DEVICE_CRYPTOCELL
+#include "objects_cryptocell.h"
+#else
+struct trng_s {
+    uint32_t placeholder;
+};
+#endif
+
 struct serial_s {
     int                 instance;
     uint32_t            tx;
@@ -134,10 +142,6 @@ struct flash_s {
     uint32_t placeholder;
 };
 
-struct trng_s {
-    uint32_t placeholder;
-};
-
 #include "gpio_object.h"
 
 #ifdef __cplusplus

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/trng_api.c

@@ -37,7 +37,7 @@
  */
 
 #if defined(DEVICE_TRNG)
-
+#if !defined(DEVICE_CRYPTOCELL)
 #include "hal/trng_api.h"
 #include "hal/critical_section_api.h"
 
@@ -119,5 +119,5 @@ int trng_get_bytes(trng_t *obj, uint8_t *output, size_t length, size_t *output_l
 
     return result;
 }
-
+#endif/* !DEVICE_CRYPTOCELL */
 #endif