net: micrel: check return value after calling platform_get_resource()

It will cause null-ptr-deref if platform_get_resource() returns NULL,
we need check the return value.

Signed-off-by: Yang Yingliang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/micrel/ks8842.c

···
 	unsigned i;
 
 	iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!iomem) {
+		dev_err(&pdev->dev, "Invalid resource\n");
+		return -EINVAL;
+	}
 	if (!request_mem_region(iomem->start, resource_size(iomem), DRV_NAME))
 		goto err_mem_region;