openvswitch: 802.1ad uapi changes.

openvswitch: Add support for 8021.AD

Change the description of the VLAN tpid field.

Signed-off-by: Thomas F Herbert <thomasfherbert@gmail.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>