net: mscc: ocelot: 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 <yangyingliang@huawei.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/ocelot/seville_vsc9953.c

@@ -1206,6 +1206,11 @@ static int seville_probe(struct platform_device *pdev)
 	felix->info = &seville_info_vsc9953;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		err = -EINVAL;
+		dev_err(&pdev->dev, "Invalid resource\n");
+		goto err_alloc_felix;
+	}
 	felix->switch_base = res->start;
 
 	ds = kzalloc(sizeof(struct dsa_switch), GFP_KERNEL);