spi: rockchip: fix probe deferral handling

Use dma_request_chan instead of dma_request_slave_channel,
in this case we can check EPROBE_DEFER without static
warning.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-rockchip.c

@@ -723,23 +723,27 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 	master->transfer_one = rockchip_spi_transfer_one;
 	master->handle_err = rockchip_spi_handle_err;
 
-	rs->dma_tx.ch = dma_request_slave_channel(rs->dev, "tx");
-	if (IS_ERR_OR_NULL(rs->dma_tx.ch)) {
+	rs->dma_tx.ch = dma_request_chan(rs->dev, "tx");
+	if (IS_ERR(rs->dma_tx.ch)) {
 		/* Check tx to see if we need defer probing driver */
 		if (PTR_ERR(rs->dma_tx.ch) == -EPROBE_DEFER) {
 			ret = -EPROBE_DEFER;
 			goto err_get_fifo_len;
 		}
 		dev_warn(rs->dev, "Failed to request TX DMA channel\n");
+		rs->dma_tx.ch = NULL;
 	}
 
-	rs->dma_rx.ch = dma_request_slave_channel(rs->dev, "rx");
-	if (!rs->dma_rx.ch) {
-		if (rs->dma_tx.ch) {
+	rs->dma_rx.ch = dma_request_chan(rs->dev, "rx");
+	if (IS_ERR(rs->dma_rx.ch)) {
+		if (PTR_ERR(rs->dma_rx.ch) == -EPROBE_DEFER) {
 			dma_release_channel(rs->dma_tx.ch);
 			rs->dma_tx.ch = NULL;
+			ret = -EPROBE_DEFER;
+			goto err_get_fifo_len;
 		}
 		dev_warn(rs->dev, "Failed to request RX DMA channel\n");
+		rs->dma_rx.ch = NULL;
 	}
 
 	if (rs->dma_tx.ch && rs->dma_rx.ch) {