macvtap: Let TUNSETOFFLOAD actually controll offload features.

When the user issues TUNSETOFFLOAD ioctl, macvtap does not do
anything other then to verify arguments.  This patch adds
functionality to allow users to actually control offload features.
NETIF_F_GSO and NETIF_F_GRO are always on, but the rest of the
features can be controlled.

Signed-off-by: Vlad Yasevich <vyasevic@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/if_macvlan.h b/include/linux/if_macvlan.h
index f49a9f6..ddd33fd 100644
--- a/include/linux/if_macvlan.h
+++ b/include/linux/if_macvlan.h
@@ -65,6 +65,7 @@
 
 	DECLARE_BITMAP(mc_filter, MACVLAN_MC_FILTER_SZ);
 
+	netdev_features_t	set_features;
 	enum macvlan_mode	mode;
 	u16			flags;
 	int (*receive)(struct sk_buff *skb);
@@ -75,6 +76,7 @@
 	struct list_head	queue_list;
 	int			numvtaps;
 	int			numqueues;
+	netdev_features_t	tap_features;
 	int			minor;
 };