spi: sirf: Use dma_request_chan() instead dma_request_slave_channel()

dma_request_slave_channel() is a wrapper on top of dma_request_chan()
eating up the error code.

By using dma_request_chan() directly the driver can support deferred
probing against DMA.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20191212135550.4634-7-peter.ujfalusi@ti.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-sirf.c

@@ -1126,16 +1126,16 @@ static int spi_sirfsoc_probe(struct platform_device *pdev)
 	sspi->bitbang.master->dev.of_node = pdev->dev.of_node;
 
 	/* request DMA channels */
-	sspi->rx_chan = dma_request_slave_channel(&pdev->dev, "rx");
-	if (!sspi->rx_chan) {
+	sspi->rx_chan = dma_request_chan(&pdev->dev, "rx");
+	if (IS_ERR(sspi->rx_chan)) {
 		dev_err(&pdev->dev, "can not allocate rx dma channel\n");
-		ret = -ENODEV;
+		ret = PTR_ERR(sspi->rx_chan);
 		goto free_master;
 	}
-	sspi->tx_chan = dma_request_slave_channel(&pdev->dev, "tx");
-	if (!sspi->tx_chan) {
+	sspi->tx_chan = dma_request_chan(&pdev->dev, "tx");
+	if (IS_ERR(sspi->tx_chan)) {
 		dev_err(&pdev->dev, "can not allocate tx dma channel\n");
-		ret = -ENODEV;
+		ret = PTR_ERR(sspi->tx_chan);
 		goto free_rx_dma;
 	}