netfilter: ebt_ip6: allow matching on ipv6-icmp types/codes

To avoid adding a new match revision icmp type/code are stored
in the sport/dport area.

Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Holger Eitzenberger <holger@eitzenberger.org>
Reviewed-by: Bart De <Schuymer&lt;bdschuym@pandora.be>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>