dmaengine: img-mdc: fix a possible NULL dereference

of_match_device could return NULL, and so cause a NULL pointer
dereference later at line 850:
mdma->soc = match->data;

For fixing this problem, we use of_device_get_match_data(), this will
simplify the code a little by using a standard function for
getting the match data.

This was reported by coverity (CID 1324134)

Signed-off-by: LABBE Corentin <clabbe.montjoie@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/img-mdc-dma.c

@@ -861,7 +861,6 @@ static int mdc_dma_probe(struct platform_device *pdev)
 {
 	struct mdc_dma *mdma;
 	struct resource *res;
-	const struct of_device_id *match;
 	unsigned int i;
 	u32 val;
 	int ret;
@@ -871,8 +870,7 @@ static int mdc_dma_probe(struct platform_device *pdev)
 		return -ENOMEM;
 	platform_set_drvdata(pdev, mdma);
 
-	match = of_match_device(mdc_dma_of_match, &pdev->dev);
-	mdma->soc = match->data;
+	mdma->soc = of_device_get_match_data(&pdev->dev);
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	mdma->regs = devm_ioremap_resource(&pdev->dev, res);