datapath: Add meter infrastructure

datapath: Add meter infrastructure

Upstream commit:
    commit 96fbc13d7e770b542d2d1fcf700d0baadc6e8063
    Author: Andy Zhou <azhou@ovn.org>
    Date:   Fri Nov 10 12:09:42 2017 -0800

    openvswitch: Add meter infrastructure

    OVS kernel datapath so far does not support Openflow meter action.
    This is the first stab at adding kernel datapath meter support.
    This implementation supports only drop band type.

    Signed-off-by: Andy Zhou <azhou@ovn.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Added a compat layer fixup for nla_parse.
Added another compat fixup for ktime_get_ns.

Cc: Andy Zhou <azhou@ovn.org>
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>