DISCO_F746NG: add bootloader support

targets/TARGET_STM/TARGET_STM32F7/TARGET_STM32F746xG/TARGET_DISCO_F746NG/system_clock.c

@@ -30,6 +30,7 @@
 **/
 
 #include "stm32f7xx.h"
+#include "nvic_addr.h"
 #include "mbed_error.h"
 
 /*!< Uncomment the following line if you need to relocate your vector Table in
@@ -92,7 +93,7 @@ void SystemInit(void)
 #ifdef VECT_TAB_SRAM
     SCB->VTOR = RAMDTCM_BASE | VECT_TAB_OFFSET; /* Vector Table Relocation in Internal SRAM */
 #else
-    SCB->VTOR = FLASH_BASE | VECT_TAB_OFFSET; /* Vector Table Relocation in Internal FLASH */
+    SCB->VTOR = NVIC_FLASH_VECTOR_ADDRESS; /* Vector Table Relocation in Internal FLASH */
 #endif
 
 }

targets/targets.json

@@ -3460,6 +3460,7 @@
         ],
         "release_versions": ["2", "5"],
         "device_name": "STM32F746NG",
+        "bootloader_supported": true,
         "overrides": {
             "network-default-interface-type": "ETHERNET"
         }