serial: meson: Use uart_xmit_advance()

Take advantage of the new uart_xmit_advance() helper.
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20221019091151.6692-23-ilpo.jarvinen@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/meson_uart.c

@@ -162,8 +162,7 @@ static void meson_uart_start_tx(struct uart_port *port)
 
 		ch = xmit->buf[xmit->tail];
 		writel(ch, port->membase + AML_UART_WFIFO);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		port->icount.tx++;
+		uart_xmit_advance(port, 1);
 	}
 
 	if (!uart_circ_empty(xmit)) {