[serial] 优化RT_USING_POSIX_TERMIOS预编译

components/drivers/serial/serial.c

@@ -1112,6 +1112,7 @@ static rt_err_t rt_serial_control(struct rt_device *dev,
             break;
         case TCXONC:
             break;
+#endif /*RT_USING_POSIX_TERMIOS*/
         case TIOCSWINSZ:
             {
                 struct winsize* p_winsize;
@@ -1202,7 +1203,6 @@ static rt_err_t rt_serial_control(struct rt_device *dev,
                 p_winsize->ws_ypixel = 0;/* unused */
             }
             break;
-#endif /*RT_USING_POSIX_TERMIOS*/
         case FIONREAD:
             {
                 rt_size_t recved = 0;