serial: men_z135_uart: Use uart_xmit_advance()

Take advantage of the new uart_xmit_advance() helper.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20221019091151.6692-3-ilpo.jarvinen@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/men_z135_uart.c

@@ -352,11 +352,8 @@ static void men_z135_handle_tx(struct men_z135_port *uart)
 	n = min(n, s);
 
 	memcpy_toio(port->membase + MEN_Z135_TX_RAM, &xmit->buf[xmit->tail], n);
-	xmit->tail = (xmit->tail + n) & (UART_XMIT_SIZE - 1);
-
 	iowrite32(n & 0x3ff, port->membase + MEN_Z135_TX_CTRL);
-
-	port->icount.tx += n;
+	uart_xmit_advance(port, n);
 
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 		uart_write_wakeup(port);