fix: zorro - date and time reset issue (#1643)

Fixes removal of battery or DFU connection causing RTC time and date  to be reset

radio/src/targets/taranis/CMakeLists.txt

@@ -193,6 +193,7 @@ elseif(PCB STREQUAL X7)
     set(FIRMWARE_TARGET_SRC
       ${FIRMWARE_TARGET_SRC}
       startup_stm32f40_41xxx.s
+      ../../thirdparty/STM32F4xx_DSP_StdPeriph_Lib_V1.8.0/Libraries/STM32F4xx_StdPeriph_Driver/src/stm32f4xx_flash.c
       )
     add_definitions(-DSTM32F40_41xxx)
     set(ROTARY_ENCODER YES)

radio/src/targets/taranis/board.cpp

@@ -135,6 +135,17 @@ void boardInit()
   bluetoothInit(BLUETOOTH_DEFAULT_BAUDRATE, true);
 #endif
 
+#if defined (RADIO_ZORRO)
+    
+  if (FLASH_OB_GetBOR() != OB_BOR_LEVEL3)
+  {
+    FLASH_OB_Unlock();
+    FLASH_OB_BORConfig(OB_BOR_LEVEL3);
+    FLASH_OB_Launch();
+    FLASH_OB_Lock();
+  }
+#endif
+
   pwrInit();
 
 #if defined(AUTOUPDATE)