net: call notifiers for mtu change even if iface is not up

Do the same thing as in set mac. Call notifiers every time.
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -4971,7 +4971,7 @@ int dev_set_mtu(struct net_device *dev, int new_mtu)
 	else
 		dev->mtu = new_mtu;
 
-	if (!err && dev->flags & IFF_UP)
+	if (!err)
 		call_netdevice_notifiers(NETDEV_CHANGEMTU, dev);
 	return err;
 }