Fix rt_serial_control() bug for customized command and indent the code

components/drivers/serial/serial.c

@@ -360,6 +360,11 @@ static rt_err_t rt_serial_control(struct rt_device *dev,
             /* configure device */
             serial->ops->configure(serial, (struct serial_configure *)args);
             break;
+
+        default :
+            /* control device */
+            serial->ops->control(serial, cmd, args);
+            break;
     }
 
     return RT_EOK;