A struct net_device always maps to zero or one vlan groups and we
always know the device when we are looking up a group.  We currently
do a hash table lookup on the device to find the group but it is
much simpler to just store a pointer.
Signed-off-by: NJesse Gross <jesse@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>