tunnel: Inherit NETIF_F_SG for hw_enc_features.

Inherit scatergather feature for tunnel devices to avoid
copy for TSO packets of tunneling device like GRE.
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -5205,6 +5205,10 @@ int register_netdevice(struct net_device *dev)
 	 */
 	dev->vlan_features |= NETIF_F_HIGHDMA;
 
+	/* Make NETIF_F_SG inheritable to tunnel devices.
+	 */
+	dev->hw_enc_features |= NETIF_F_SG;
+
 	ret = call_netdevice_notifiers(NETDEV_POST_INIT, dev);
 	ret = notifier_to_errno(ret);
 	if (ret)