This patch adds the missing bits to allow to match per meta l4proto from
the bridge. Example:

  nft add rule bridge filter input ether type {ip, ip6} meta l4proto udp counter
Signed-off-by: NAlvaro Neira Ayuso <alvaroneay@gmail.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>