ebtables: Allow filtering of hardware accelerated vlan frames.

An upcoming commit will allow packets with hardware vlan acceleration
information to be passed though more parts of the network stack, including
packets trunked through the bridge.  This adds support for matching and
filtering those packets through ebtables.

Signed-off-by: Jesse Gross <jesse@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>