loopback: make use of NETIF_F_GSO_SOFTWARE

NETIF_F_GSO_SOFTWARE was defined to list all GSO software types, so lets
make use of it in loopback code. Note that veth/vxlan/others already
uses it.

Within this patch series, this patch causes lo to pick up SCTP GSO feature
automatically (as it's added to NETIF_F_GSO_SOFTWARE) and thus avoiding
segmentation if possible.
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/loopback.c

@@ -169,10 +169,9 @@ static void loopback_setup(struct net_device *dev)
 	dev->flags		= IFF_LOOPBACK;
 	dev->priv_flags		|= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
 	netif_keep_dst(dev);
-	dev->hw_features	= NETIF_F_ALL_TSO | NETIF_F_UFO;
+	dev->hw_features	= NETIF_F_GSO_SOFTWARE;
 	dev->features 		= NETIF_F_SG | NETIF_F_FRAGLIST
-		| NETIF_F_ALL_TSO
-		| NETIF_F_UFO
+		| NETIF_F_GSO_SOFTWARE
 		| NETIF_F_HW_CSUM
 		| NETIF_F_RXCSUM
 		| NETIF_F_SCTP_CRC