vlan: Optimize multiple unregistration

Use unregister_netdevice_many() to speedup master device unregister.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index 8898cbe..71a4870 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -85,6 +85,7 @@
 					    * the vlan is attached to.
 					    */
 	unsigned int		nr_vlans;
+	int			killall;
 	struct hlist_node	hlist;	/* linked list */
 	struct net_device **vlan_devices_arrays[VLAN_GROUP_ARRAY_SPLIT_PARTS];
 	struct rcu_head		rcu;