compat: add compatibility headers for tc mpls action
OvS includes compat code for several TC actions including vlan, mirred and
tunnel key. MPLS actions have recently been added to TC in the kernel. In
preparation for adding TC offload code for MPLS, add the MPLS compat code.
Signed-off-by: John Hurley <john.hurley@netronome.com> Reviewed-by: Simon Horman <simon.horman@netronome.com> Signed-off-by: Simon Horman <simon.horman@netronome.com>