dmaengine: sprd: Fix potential NULL dereference in sprd_dma_probe()

platform_get_resource() may fail and return NULL, so we should
better check it's return value to avoid a NULL pointer dereference
a bit later in the code.

This is detected by Coccinelle semantic patch.

@@
expression pdev, res, n, t, e, e1, e2;
@@

res = platform_get_resource(pdev, t, n);
+ if (!res)
+   return -EINVAL;
... when != res == NULL
e = devm_ioremap_nocache(e1, res->start, e2);

Fixes: 9b3b8171 ("dmaengine: sprd: Add Spreadtrum DMA driver")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/sprd-dma.c

@@ -807,6 +807,8 @@ static int sprd_dma_probe(struct platform_device *pdev)
 	}
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
 	sdev->glb_base = devm_ioremap_nocache(&pdev->dev, res->start,
 					      resource_size(res));
 	if (!sdev->glb_base)