serial: linflexuart: 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/20221019091151.6692-16-ilpo.jarvinen@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/fsl_linflexuart.c

@@ -178,8 +178,7 @@ static inline void linflex_transmit_buffer(struct uart_port *sport)
 
 	while (!uart_circ_empty(xmit)) {
 		linflex_put_char(sport, xmit->buf[xmit->tail]);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		sport->icount.tx++;
+		uart_xmit_advance(sport, 1);
 	}
 
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)