nbd: remove bogus BUG_ON in NBD_CLEAR_QUE

The NBD_CLEAR_QUE ioctl has been deprecated for quite some time (its job
is now done by two other ioctls).  We should stop trying to make bogus
assertions in it.  Also, user-level code should remove calls to
NBD_CLEAR_QUE, ASAP.

Signed-off-by: Michal Belczyk <belczyk@bsd.krakow.pl>
Signed-off-by: Paul Clements <paul.clements@steeleye.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 46b35f7..7ed1308 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -751,7 +751,6 @@
 		 * This is for compatibility only.  The queue is always cleared
 		 * by NBD_DO_IT or NBD_CLEAR_SOCK.
 		 */
-		BUG_ON(!nbd->sock && !list_empty(&nbd->queue_head));
 		return 0;
 
 	case NBD_PRINT_DEBUG: