netfilter: bridge-netfilter: cleanup br_netfilter.c

bridge-netfilter: cleanup br_netfilter.c

- remove some of the graffiti at the head of br_netfilter.c
- remove __br_dnat_complain()
- remove KERN_INFO messages when CONFIG_NETFILTER_DEBUG is defined

Signed-off-by: Bart De Schuymer <bdschuym@pandora.be>
Signed-off-by: Patrick McHardy <kaber@trash.net>