[NETFILTER]: nfnetlink_log: fix crash on bridged packet
physoutdev is only set on purely bridged packet, when nfnetlink_log is used
in the OUTPUT/FORWARD/POSTROUTING hooks on packets forwarded from or to a
bridge it crashes when trying to dereference skb->nf_bridge->physoutdev.
Reported by Holger Eitzenberger <heitzenberger@astaro.com>
Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>