datapath: Clear the L4 portion of the key for "later" fragments

datapath: Clear the L4 portion of the key for "later" fragments

Upstream commit:
    commit 0754b4e8cdf3eec6e4122e79af26ed9bab20f8f8
    Author: Justin Pettit <jpettit@ovn.org>
    Date:   Tue Aug 27 07:58:10 2019 -0700

    openvswitch: Clear the L4 portion of the key for "later" fragments.

    Only the first fragment in a datagram contains the L4 headers.  When the
    Open vSwitch module parses a packet, it always sets the IP protocol
    field in the key, but can only set the L4 fields on the first fragment.
    The original behavior would not clear the L4 portion of the key, so
    garbage values would be sent in the key for "later" fragments.  This
    patch clears the L4 fields in that circumstance to prevent sending those
    garbage values as part of the upcall.

    Signed-off-by: Justin Pettit <jpettit@ovn.org>
    Acked-by: Pravin B Shelar <pshelar@ovn.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Justin Pettit <jpettit@ovn.org>