net: move is_vlan_dev into public header file (v2)

Migrate is_vlan_dev() to if_vlan.h so that core networkig can use it

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: davem@davemloft.net
CC: bhutchings@solarflare.com
Signed-off-by: David S. Miller <davem@davemloft.net>

net/8021q/vlan.h

@@ -118,11 +118,6 @@ extern void vlan_netlink_fini(void);
 
 extern struct rtnl_link_ops vlan_link_ops;
 
-static inline int is_vlan_dev(struct net_device *dev)
-{
-	return dev->priv_flags & IFF_802_1Q_VLAN;
-}
-
 extern int vlan_net_id;
 
 struct proc_dir_entry;