vrf: simplify the netdev notifier function

We can drop the check because if vrf_ptr is present then we must have
the vrf device as a master and since we're running with rtnl it can't go
away.
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vrf.c

@@ -624,8 +624,7 @@ static int vrf_device_event(struct notifier_block *unused,
 		if (!vrf_ptr || netif_is_vrf(dev))
 			goto out;
 
-		vrf_dev = __dev_get_by_index(dev_net(dev), vrf_ptr->ifindex);
-		if (vrf_dev)
+		vrf_dev = netdev_master_upper_dev_get(dev);
 		vrf_del_slave(vrf_dev, dev);
 	}
 out: