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>
get_actions_from_instruction(const struct ofp11_instruction *inst,
                             const struct ofp_action_header **actions,
                             size_t *actions_len)
{
    *actions = ALIGNED_CAST(const struct ofp_action_header *, inst + 1);
    *actions_len = ntohs(inst->len) - sizeof *inst;
}

get_actions_from_instruction(const struct ofp11_instruction *inst,
                             const struct ofp_action_header **actions,
                             size_t *actions_len)
{
    *actions = ALIGNED_CAST(const struct ofp_action_header *, inst + 1);
    *actions_len = ntohs(inst->len) - sizeof *inst;
}
