serial: fsl_lpuart: 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/20221019091151.6692-17-ilpo.jarvinen@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/fsl_lpuart.c

@@ -535,9 +535,7 @@ static void lpuart_dma_tx_complete(void *arg)
 	dma_unmap_sg(chan->device->dev, sgl, sport->dma_tx_nents,
 		     DMA_TO_DEVICE);
 
-	xmit->tail = (xmit->tail + sport->dma_tx_bytes) & (UART_XMIT_SIZE - 1);
-
-	sport->port.icount.tx += sport->dma_tx_bytes;
+	uart_xmit_advance(&sport->port, sport->dma_tx_bytes);
 	sport->dma_tx_in_progress = false;
 	spin_unlock_irqrestore(&sport->port.lock, flags);
 
@@ -772,8 +770,7 @@ static inline void lpuart32_transmit_buffer(struct lpuart_port *sport)
 	txcnt &= UARTWATER_COUNT_MASK;
 	while (!uart_circ_empty(xmit) && (txcnt < sport->txfifo_size)) {
 		lpuart32_write(&sport->port, xmit->buf[xmit->tail], UARTDATA);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		sport->port.icount.tx++;
+		uart_xmit_advance(&sport->port, 1);
 		txcnt = lpuart32_read(&sport->port, UARTWATER);
 		txcnt = txcnt >> UARTWATER_TXCNT_OFF;
 		txcnt &= UARTWATER_COUNT_MASK;