MAGIC value for powerReason should be stored in RTC backup on Horus (#7096)

- Allows the radio main application to start correctly when coming from an app in RAM
- Refactoring of the `UNEXPECTED_SHUTDOWN()` process
- Saves the RTC battery as BACKUP RAM is not needed on normal shutdown
- On PWR OFF on an ALERT, the radio won't show the next alert before shutting down
- Bootloader flashable through the SD Manager

radio/src/io/frsky_firmware_update.cpp

@@ -492,7 +492,7 @@ const char * FrskyDeviceFirmwareUpdate::flashFirmware(const char * filename)
   drawProgressScreen(getBasename(filename), STR_DEVICE_RESET, 0, 0);
 
   /* wait 2s off */
-  watchdogSuspend(2000);
+  watchdogSuspend(1000 /*10s*/);
   RTOS_WAIT_MS(2000);
 
   const char * result = doFlashFirmware(filename);
@@ -515,7 +515,7 @@ const char * FrskyDeviceFirmwareUpdate::flashFirmware(const char * filename)
   SPORT_UPDATE_POWER_OFF();
 
   /* wait 2s off */
-  watchdogSuspend(2000);
+  watchdogSuspend(500 /*5s*/);
   RTOS_WAIT_MS(2000);
   telemetryClearFifo();
 
@@ -756,7 +756,7 @@ const char * FrskyChipFirmwareUpdate::flashFirmware(const char * filename, bool
 
   if (wait) {
     /* wait 2s off */
-    watchdogSuspend(2000);
+    watchdogSuspend(1000 /*10s*/);
     RTOS_WAIT_MS(2000);
   }
 
@@ -776,7 +776,7 @@ const char * FrskyChipFirmwareUpdate::flashFirmware(const char * filename, bool
   }
 
   /* wait 2s off */
-  watchdogSuspend(2000);
+  watchdogSuspend(1000 /*10s*/);
   RTOS_WAIT_MS(2000);
 
 #if defined(HARDWARE_INTERNAL_MODULE)