odp-execute: Fix length checking while executing check_pkt_len action.

odp-execute: Fix length checking while executing check_pkt_len action.

If dp-packet contains l2 padding or cutlen was applied to it, size will
be larger than the actual size of a payload and action will work
incorrectly.

Ex. Padding could be added during miniflow_extract() if detected.

Fixes: 5b34f8fc3b38 ("Add a new OVS action check_pkt_larger")
Reported-by: Miroslav Kubiczek <miroslav.kubiczek@adaptivemobile.com>
Reported-at: https://mail.openvswitch.org/pipermail/ovs-discuss/2020-May/050157.html
Acked-by: Dumitru Ceara <dceara@redhat.com>
Acked-by: Flavio Leitner <fbl@sysclose.org>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>