media: xilinx: 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>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/platform/xilinx/xilinx-dma.c

@@ -725,10 +725,11 @@ int xvip_dma_init(struct xvip_composite_device *xdev, struct xvip_dma *dma,
 
 	/* ... and the DMA channel. */
 	snprintf(name, sizeof(name), "port%u", port);
-	dma->dma = dma_request_slave_channel(dma->xdev->dev, name);
-	if (dma->dma == NULL) {
+	dma->dma = dma_request_chan(dma->xdev->dev, name);
+	if (IS_ERR(dma->dma)) {
+		ret = PTR_ERR(dma->dma);
+		if (ret != -EPROBE_DEFER)
 			dev_err(dma->xdev->dev, "no VDMA channel found\n");
-		ret = -ENODEV;
 		goto error;
 	}
 
@@ -752,7 +753,7 @@ void xvip_dma_cleanup(struct xvip_dma *dma)
 	if (video_is_registered(&dma->video))
 		video_unregister_device(&dma->video);
 
-	if (dma->dma)
+	if (!IS_ERR_OR_NULL(dma->dma))
 		dma_release_channel(dma->dma);
 
 	media_entity_cleanup(&dma->video.entity);