net: enable GRO by default for vlan devices

Currently vlan devices don't have GRO by default as none of the Ethernet
drivers add NETIF_F_GRO to their vlan_features.

As GRO is a software feature add GRO to dev->vlan_features in
register_netdevice() and let vlan_dev_init() take care that it gets
enabled only when dev->features has NETIF_F_GRO too.
Signed-off-by: Brandon Philips <bphilips@suse.de>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -5057,6 +5057,11 @@ int register_netdevice(struct net_device *dev)
 	if (dev->features & NETIF_F_SG)
 		dev->features |= NETIF_F_GSO;
 
+	/* Enable GRO for vlans by default if dev->features has GRO also.
+	 * vlan_dev_init() will do the dev->features check.
+	 */
+	dev->vlan_features |= NETIF_F_GRO;
+
 	ret = call_netdevice_notifiers(NETDEV_POST_INIT, dev);
 	ret = notifier_to_errno(ret);
 	if (ret)