netfilter: bridge: NF_CONNTRACK_BRIDGE does not depend on NF_TABLES_BRIDGE

Place NF_CONNTRACK_BRIDGE away from the NF_TABLES_BRIDGE dependency.

Fixes: 3c171f49

 ("netfilter: bridge: add connection tracking system")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>