NET: wan/x25_asy, move lapb_unregister to x25_asy_close_tty

We register lapb when tty is created, but unregister it only when the
device is UP. So move the lapb_unregister to x25_asy_close_tty after
the device is down.

The old behaviour causes ldisc switching to fail each second attempt,
because we noted for us that the device is unused, so we use it the
second time, but labp layer still have it registered, so it fails
obviously.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Sergey Lapin <slapin@ossfans.org>
Cc: Andrew Hendry <andrew.hendry@gmail.com>
Tested-by: Sergey Lapin <slapin@ossfans.org>
Tested-by: Mikhail Ulyanov <ulyanov.mikhail@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/x25_asy.c

@@ -498,7 +498,6 @@ static int x25_asy_open(struct net_device *dev)
 static int x25_asy_close(struct net_device *dev)
 {
 	struct x25_asy *sl = netdev_priv(dev);
-	int err;
 
 	spin_lock(&sl->lock);
 	if (sl->tty)
@@ -507,10 +506,6 @@ static int x25_asy_close(struct net_device *dev)
 	netif_stop_queue(dev);
 	sl->rcount = 0;
 	sl->xleft  = 0;
-	err = lapb_unregister(dev);
-	if (err != LAPB_OK)
-		printk(KERN_ERR "x25_asy_close: lapb_unregister error -%d\n",
-			err);
 	spin_unlock(&sl->lock);
 	return 0;
 }
@@ -595,6 +590,7 @@ static int x25_asy_open_tty(struct tty_struct *tty)
 static void x25_asy_close_tty(struct tty_struct *tty)
 {
 	struct x25_asy *sl = tty->disc_data;
+	int err;
 
 	/* First make sure we're connected. */
 	if (!sl || sl->magic != X25_ASY_MAGIC)
@@ -605,6 +601,11 @@ static void x25_asy_close_tty(struct tty_struct *tty)
 		dev_close(sl->dev);
 	rtnl_unlock();
 
+	err = lapb_unregister(sl->dev);
+	if (err != LAPB_OK)
+		printk(KERN_ERR "x25_asy_close: lapb_unregister error -%d\n",
+			err);
+
 	tty->disc_data = NULL;
 	sl->tty = NULL;
 	x25_asy_free(sl);