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>
ofpact_put_reg_load(struct ofpbuf *ofpacts, const struct mf_field *field,
                    const void *value, const void *mask)
{
    struct ofpact_set_field *sf = ofpact_put_set_field(ofpacts, field, value,
                                                       mask);
    sf->ofpact.raw = NXAST_RAW_REG_LOAD;

    return sf;
}

ofpact_put_reg_load(struct ofpbuf *ofpacts, const struct mf_field *field,
                    const void *value, const void *mask)
{
    struct ofpact_set_field *sf = ofpact_put_set_field(ofpacts, field, value,
                                                       mask);
    sf->ofpact.raw = NXAST_RAW_REG_LOAD;

    return sf;
}
