fix warning for device os none

demos/device/src/main.c

@@ -108,8 +108,6 @@ int main(void)
   #error need to start RTOS schduler
 #endif
 
-  while(1) { } // should not reach here
-
   return 0;
 }
 
@@ -133,7 +131,9 @@ OSAL_TASK_FUNCTION( led_blinking_task ) (void* p_task_para)
   board_leds(led_on_mask, 1 - led_on_mask);
   led_on_mask = 1 - led_on_mask; // toggle
 
-  uint32_t btn_mask = board_buttons();
+  uint32_t btn_mask;
+  btn_mask = board_buttons();
+	
   for(uint8_t i=0; i<32; i++)
   {
     if ( BIT_TEST_(btn_mask, i) ) printf("button %d is pressed\n", i);