[serial.c] 修复在没有开启ulog时，警告日志不会输出的问题

components/drivers/serial/serial.c

@@ -333,7 +333,7 @@ static void _serial_check_buffer_size(void)
 
     if (already_output == RT_FALSE)
     {
-#if defined(ULOG_USING_ISR_LOG)
+#if !defined(RT_USING_ULOG) || defined(ULOG_USING_ISR_LOG)
         LOG_W("Warning: There is no enough buffer for saving data,"
               " please increase the RT_SERIAL_RB_BUFSZ option.");
 #endif