serial: 8250_dma: Switch to using tty_port

The tty buffer functions are converted to using tty_port
structure instead of struct tty, so we must do the same.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_dma.c

@@ -43,8 +43,9 @@ static void __dma_rx_complete(void *param)
 {
 	struct uart_8250_port	*p = param;
 	struct uart_8250_dma	*dma = p->dma;
-	struct tty_struct	*tty = p->port.state->port.tty;
+	struct tty_port		*tty_port = &p->port.state->port;
 	struct dma_tx_state	state;
+	int			count;
 
 	dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,
 				dma->rx_size, DMA_FROM_DEVICE);
@@ -52,10 +53,12 @@ static void __dma_rx_complete(void *param)
 	dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
 	dmaengine_terminate_all(dma->rxchan);
 
-	tty_insert_flip_string(tty, dma->rx_buf, dma->rx_size - state.residue);
-	p->port.icount.rx += dma->rx_size - state.residue;
+	count = dma->rx_size - state.residue;
 
-	tty_flip_buffer_push(tty);
+	tty_insert_flip_string(tty_port, dma->rx_buf, count);
+	p->port.icount.rx += count;
+
+	tty_flip_buffer_push(tty_port);
 }
 
 int serial8250_tx_dma(struct uart_8250_port *p)