serial: atmel: Use uart_xmit_advance()

Take advantage of the new uart_xmit_advance() helper.

Reviewed-by: Claudiu Beznea <[e-mail]>
Acked-By: Richard GENOUD <[e-mail]>
Signed-off-by: Ilpo Järvinen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/atmel_serial.c

···
 
 	if (chan)
 		dmaengine_terminate_all(chan);
-	xmit->tail += atmel_port->tx_len;
-	xmit->tail &= UART_XMIT_SIZE - 1;
-
-	port->icount.tx += atmel_port->tx_len;
+	uart_xmit_advance(port, atmel_port->tx_len);
 
 	spin_lock_irq(&atmel_port->lock_tx);
 	async_tx_ack(atmel_port->desc_tx);
···
 	/* nothing left to transmit? */
 	if (atmel_uart_readl(port, ATMEL_PDC_TCR))
 		return;
-
-	xmit->tail += pdc->ofs;
-	xmit->tail &= UART_XMIT_SIZE - 1;
-
-	port->icount.tx += pdc->ofs;
+	uart_xmit_advance(port, pdc->ofs);
 	pdc->ofs = 0;
 
 	/* more to transmit - setup next transfer */