[NETFILTER] bridge: debug message fixes

If CONFIG_NETFILTER_DEBUG is enabled, it shouldn't change the
actions of the filtering. The message about skb->dst being NULL
is commonly triggered by dhclient, so it is useless. Make sure all
messages end in newline.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>