datapath: backport: vlan: Check for vlan ethernet types for 8021.q or 802.1ad

datapath: backport: vlan: Check for vlan ethernet types for 8021.q or 802.1ad

Upstream commit:
    commit fe19c4f971a55cea3be442d8032a5f6021702791
    Author: Eric Garver <e@erig.me>
    Date:   Wed Sep 7 12:56:58 2016 -0400

    This is to simplify using double tagged vlans. This function allows all
    valid vlan ethertypes to be checked in a single function call.
    Also replace some instances that check for both ETH_P_8021Q and
    ETH_P_8021AD.

    Patch based on one originally by Thomas F Herbert.

    Signed-off-by: Thomas F Herbert <thomasfherbert@gmail.com>
    Signed-off-by: Eric Garver <e@erig.me>
    Acked-by: Pravin B Shelar <pshelar@ovn.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Yi Yang <yi.y.yang@intel.com>
Acked-by: Eric Garver <e@erig.me>
Signed-off-by: Joe Stringer <joe@ovn.org>