netfilter: egress: avoid a lockdep splat

netfilter: egress: avoid a lockdep splat

include/linux/netfilter_netdev.h:97 suspicious rcu_dereference_check() usage!
2 locks held by sd-resolve/1100:
 0: ..(rcu_read_lock_bh){1:3}, at: ip_finish_output2
 1: ..(rcu_read_lock_bh){1:3}, at: __dev_queue_xmit
 __dev_queue_xmit+0 ..

The helper has two callers, one uses rcu_read_lock, the other
rcu_read_lock_bh().  Annotate the dereference to reflect this.

Fixes: 42df6e1d221dd ("netfilter: Introduce egress hook")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>