datapath: correctly fragment packet with mpls headers

datapath: correctly fragment packet with mpls headers

Upstream commit:
    commit c66549ffd666605831abf6cf19ce0571ad868e39
    Author: Jiri Benc <jbenc@redhat.com>
    Date:   Wed Oct 5 15:01:57 2016 +0200

    openvswitch: correctly fragment packet with mpls headers

    If mpls headers were pushed to a defragmented packet, the refragmentation no
    longer works correctly after 48d2ab609b6b ("net: mpls: Fixups for GSO"). The
    network header has to be shifted after the mpls headers for the
    fragmentation and restored afterwards.

    Fixes: 48d2ab609b6b ("net: mpls: Fixups for GSO")
    Signed-off-by: Jiri Benc <jbenc@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Yi-Hung Wei <yihung.wei@gmail.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>