Sub: log GPS detection state to DF on log startup

ArduSub/Log.cpp

@@ -462,6 +462,7 @@ void Sub::Log_Write_Vehicle_Startup_Messages()
     // only 200(?) bytes are guaranteed by DataFlash
     DataFlash.Log_Write_Mode(control_mode, control_mode_reason);
     Log_Write_Home_And_Origin();
+    gps.Write_DataFlash_Log_Startup_messages();
 }