AP_Bootloader: allow flash to be unprotected from the bootloader

Tools/AP_Bootloader/AP_Bootloader.cpp

@@ -76,6 +76,10 @@ int main(void)
     AFIO->MAPR = mapr | AFIO_MAPR_CAN_REMAP_REMAP2 | AFIO_MAPR_SPI3_REMAP;
 #endif
 
+#ifdef HAL_FLASH_PROTECTION
+    stm32_flash_unprotect_flash();
+#endif
+
 #ifndef NO_FASTBOOT
     enum rtc_boot_magic m = check_fast_reboot();
     bool was_watchdog = stm32_was_watchdog_reset();