ofp-actions: Avoid buffer overread in BUNDLE action decoding.

Reported-at: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=9052
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Justin Pettit <jpettit@ovn.org>
encode_POP_MPLS(const struct ofpact_pop_mpls *pop_mpls,
                enum ofp_version ofp_version, struct ofpbuf *out)
{
    put_OFPAT_POP_MPLS(out, ofp_version, pop_mpls->ethertype);
}

encode_POP_MPLS(const struct ofpact_pop_mpls *pop_mpls,
                enum ofp_version ofp_version, struct ofpbuf *out)
{
    put_OFPAT_POP_MPLS(out, ofp_version, pop_mpls->ethertype);
}
