lldp: validate a bit more received LLDP frames

lldp: validate a bit more received LLDP frames

Upstream commit:
    commit 3aeae72b97716fddac290634fad02b952d981f17
    Author: Vincent Bernat <vincent@bernat.ch>
    Date:   Tue, 1 Oct 2019 21:42:42 +0200

    lldp: validate a bit more received LLDP frames

    Notably, we ensure the order and unicity of Chassis ID, Port ID and
    TTL TLV. For Chassis ID and Port ID, we also ensure the maximum size
    does not exceed 256.

    Fix https://github.com/vincentbernat/lldpd/issues/351

Fixes: be53a5c447c3 ("auto-attach: Initial support for Auto-Attach standard")
Signed-off-by: Aaron Conole <aconole@redhat.com>
Co-authored-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>