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>
format_STACK_PUSH(const struct ofpact_stack *a, struct ds *s)
{
    nxm_format_stack_push(a, s);
}

format_STACK_PUSH(const struct ofpact_stack *a, struct ds *s)
{
    nxm_format_stack_push(a, s);
}
