net: vlan, qlcnic: make vlan_find_dev private

there is only one user of vlan_find_dev outside of the actual vlan code:
qlcnic uses it to iterate over some VLANs it knows.

let's just make vlan_find_dev private to the VLAN code and have the
iteration in qlcnic be a bit more direct. (a few rcu dereferences less
too)

Signed-off-by: David Lamparter <equinox@diac24.net>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Amit Kumar Salecha <amit.salecha@qlogic.com>
Cc: Anirban Chakraborty <anirban.chakraborty@qlogic.com>
Cc: linux-driver@qlogic.com
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/8021q/vlan.h b/net/8021q/vlan.h
index 9da07e3..b132f54 100644
--- a/net/8021q/vlan.h
+++ b/net/8021q/vlan.h
@@ -74,6 +74,18 @@
 	return netdev_priv(dev);
 }
 
+/* Must be invoked with rcu_read_lock or with RTNL. */
+static inline struct net_device *vlan_find_dev(struct net_device *real_dev,
+					       u16 vlan_id)
+{
+	struct vlan_group *grp = rcu_dereference_rtnl(real_dev->vlgrp);
+
+	if (grp)
+		return vlan_group_get_device(grp, vlan_id);
+
+	return NULL;
+}
+
 /* found in vlan_dev.c */
 void vlan_dev_set_ingress_priority(const struct net_device *dev,
 				   u32 skb_prio, u16 vlan_prio);