datapath: add processing of L3 packets

datapath: add processing of L3 packets

Upstream commit:
    commit 5108bbaddc37c1c8583f0cf2562d7d3463cd12cb
    Author: Jiri Benc <jbenc@redhat.com>
    Date:   Thu Nov 10 16:28:21 2016 +0100

    openvswitch: add processing of L3 packets

    Support receiving, extracting flow key and sending of L3 packets (packets
    without an Ethernet header).

    Note that even after this patch, non-Ethernet interfaces are still not
    allowed to be added to bridges. Similarly, netlink interface for sending and
    receiving L3 packets to/from user space is not in place yet.

    Based on previous versions by Lorand Jakab and Simon Horman.

    Signed-off-by: Lorand Jakab <lojakab@cisco.com>
    Signed-off-by: Simon Horman <simon.horman@netronome.com>
    Signed-off-by: Jiri Benc <jbenc@redhat.com>
    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>
Signed-off-by: Joe Stringer <joe@ovn.org>