serial: mxs-auart: convert not to use dma_request_slave_channel()

dma_request_slave_channel() is deprecated. dma_request_chan() should
be used directly instead.

Switch to the preferred function and update the error handling accordingly.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/94812f7063e4db5590254ec45fe9bb3c6569509e.1700410918.git.christophe.jaillet@wanadoo.frSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/mxs-auart.c

@@ -904,21 +904,27 @@ static void mxs_auart_dma_exit(struct mxs_auart_port *s)
 
 static int mxs_auart_dma_init(struct mxs_auart_port *s)
 {
+	struct dma_chan *chan;
+
 	if (auart_dma_enabled(s))
 		return 0;
 
 	/* init for RX */
-	s->rx_dma_chan = dma_request_slave_channel(s->dev, "rx");
-	if (!s->rx_dma_chan)
+	chan = dma_request_chan(s->dev, "rx");
+	if (IS_ERR(chan))
 		goto err_out;
+	s->rx_dma_chan = chan;
+
 	s->rx_dma_buf = kzalloc(UART_XMIT_SIZE, GFP_KERNEL | GFP_DMA);
 	if (!s->rx_dma_buf)
 		goto err_out;
 
 	/* init for TX */
-	s->tx_dma_chan = dma_request_slave_channel(s->dev, "tx");
-	if (!s->tx_dma_chan)
+	chan = dma_request_chan(s->dev, "tx");
+	if (IS_ERR(chan))
 		goto err_out;
+	s->tx_dma_chan = chan;
+
 	s->tx_dma_buf = kzalloc(UART_XMIT_SIZE, GFP_KERNEL | GFP_DMA);
 	if (!s->tx_dma_buf)
 		goto err_out;