serial: atmel: 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/f2e9790d8b49aeba8b43ce018d30a35b837ac1eb.1700409299.git.christophe.jaillet@wanadoo.frSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/atmel_serial.c

@@ -1013,14 +1013,18 @@ static int atmel_prepare_tx_dma(struct uart_port *port)
 	struct device *mfd_dev = port->dev->parent;
 	dma_cap_mask_t		mask;
 	struct dma_slave_config config;
+	struct dma_chan *chan;
 	int ret, nent;
 
 	dma_cap_zero(mask);
 	dma_cap_set(DMA_SLAVE, mask);
 
-	atmel_port->chan_tx = dma_request_slave_channel(mfd_dev, "tx");
-	if (atmel_port->chan_tx == NULL)
+	chan = dma_request_chan(mfd_dev, "tx");
+	if (IS_ERR(chan)) {
+		atmel_port->chan_tx = NULL;
 		goto chan_err;
+	}
+	atmel_port->chan_tx = chan;
 	dev_info(port->dev, "using %s for tx DMA transfers\n",
 		dma_chan_name(atmel_port->chan_tx));
 
@@ -1188,6 +1192,7 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
 	dma_cap_mask_t		mask;
 	struct dma_slave_config config;
 	struct circ_buf		*ring;
+	struct dma_chan *chan;
 	int ret, nent;
 
 	ring = &atmel_port->rx_ring;
@@ -1195,9 +1200,12 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
 	dma_cap_zero(mask);
 	dma_cap_set(DMA_CYCLIC, mask);
 
-	atmel_port->chan_rx = dma_request_slave_channel(mfd_dev, "rx");
-	if (atmel_port->chan_rx == NULL)
+	chan = dma_request_chan(mfd_dev, "rx");
+	if (IS_ERR(chan)) {
+		atmel_port->chan_rx = NULL;
 		goto chan_err;
+	}
+	atmel_port->chan_rx = chan;
 	dev_info(port->dev, "using %s for rx DMA transfers\n",
 		dma_chan_name(atmel_port->chan_rx));