[VLAN]: Fix OOPS on module removal.

The current code attempts to add a proc entry for each vlan device,
however there is no check whether this attempt succeeded. When a device
is unregistered it tries to remove the proc entry, if none was added
the oops follows...

net/8021q/vlan.c

@@ -547,7 +547,9 @@ static struct net_device *register_vlan_device(const char *eth_IF_name,
 	    
 	grp->vlan_devices[VLAN_ID] = new_dev;
 
-	vlan_proc_add_dev(new_dev); /* create it's proc entry */
+	if (vlan_proc_add_dev(new_dev)<0)/* create it's proc entry */
+            	printk(KERN_WARNING "VLAN: failed to add proc entry for %s\n",
+					                 new_dev->name);
 
 	if (real_dev->features & NETIF_F_HW_VLAN_FILTER)
 		real_dev->vlan_rx_add_vid(real_dev, VLAN_ID);

net/8021q/vlanproc.c

@@ -228,8 +228,10 @@ int vlan_proc_rem_dev(struct net_device *vlandev)
 #endif
 
 	/** NOTE:  This will consume the memory pointed to by dent, it seems. */
-	remove_proc_entry(VLAN_DEV_INFO(vlandev)->dent->name, proc_vlan_dir);
-	VLAN_DEV_INFO(vlandev)->dent = NULL;
+	if (VLAN_DEV_INFO(vlandev)->dent) {
+		remove_proc_entry(VLAN_DEV_INFO(vlandev)->dent->name, proc_vlan_dir);
+		VLAN_DEV_INFO(vlandev)->dent = NULL;
+	}
 
 	return 0;
 }