atm: Bad locking on br2684_devs modifications.

The list_del happens under read-locked devs_lock.

Signed-off-by: Pavel Emelyanov <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/atm/br2684.c

···
 		/* skb==NULL means VCC is being destroyed */
 		br2684_close_vcc(brvcc);
 		if (list_empty(&brdev->brvccs)) {
-			read_lock(&devs_lock);
+			write_lock_irq(&devs_lock);
 			list_del(&brdev->br2684_devs);
-			read_unlock(&devs_lock);
+			write_unlock_irq(&devs_lock);
 			unregister_netdev(net_dev);
 		}
 		return;