net: remove some sparse warnings

netdev_adjacent_add_links() and netdev_adjacent_del_links()
are static.

queue->qdisc has __rcu annotation, need to use RCU_INIT_POINTER()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>