[NETFILTER]: bridge netfilter: remove nf_bridge_info read-only netoutdev member

Before the removal of the deferred output hooks, netoutdev was used in
case of VLANs on top of a bridge to store the VLAN device, so the
deferred hooks would see the correct output device. This isn't
necessary anymore since we're calling the output hooks for the correct
device directly in the IP stack.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>