net/sched: act_vlan: Add {POP,PUSH}_ETH actions

    Implement TCA_VLAN_ACT_POP_ETH and TCA_VLAN_ACT_PUSH_ETH, to
    respectively pop and push a base Ethernet header at the beginning of a
    frame.

    POP_ETH is just a matter of pulling ETH_HLEN bytes. VLAN tags, if any,
    must be stripped before calling POP_ETH.

    PUSH_ETH is restricted to skbs with no mac_header, and only the MAC
    addresses can be configured. The Ethertype is automatically set from
    skb->protocol. These restrictions ensure that all skb's fields remain
    consistent, so that this action can't confuse other part of the
    networking stack (like GSO).

    Since openvswitch already had these actions, consolidate the code in
    skbuff.c (like for vlan and mpls push/pop).

Change-Id: Ifce1d5fee3eb1741bdc88b22f9000226744cc56c
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Git-commit: 19fbcb36a39eefbe8912a13ccc02e937b1c418d6
Git-repo: https://android.googlesource.com/kernel/common/


[quic_jguidry@quicinc.com: Added CONFIG_NET_SCHED_ACT_VLAN_QGKI to
 sdxlemur.config]
Signed-off-by: James Wyatt Guidry <quic_jguidry@quicinc.com>