net: bcmgenet: 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: NYang Yingliang <yangyingliang@huawei.com>
Acked-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/genet/bcmmii.c

@@ -423,6 +423,10 @@ static int bcmgenet_mii_register(struct bcmgenet_priv *priv)
 	int id, ret;
 
 	pres = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!pres) {
+		dev_err(&pdev->dev, "Invalid resource\n");
+		return -EINVAL;
+	}
 	memset(&res, 0, sizeof(res));
 	memset(&ppd, 0, sizeof(ppd));