meta: introduce meta ibrhwaddr support

meta: introduce meta ibrhwaddr support

Can be used in bridge prerouting hook to redirect the packet to the
receiving physical device for processing.

table bridge nat {
        chain PREROUTING {
                type filter hook prerouting priority 0; policy accept;
                ether daddr de:ad:00:00:be:ef meta pkttype set host ether daddr set meta ibrhwaddr accept
        }
}

Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Signed-off-by: Florian Westphal <fw@strlen.de>