dm: don't use idr_remove_all()

idr_destroy() can destroy idr by itself and idr_remove_all() is being
deprecated.  Drop its usage.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Alasdair Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/md/dm.c

@@ -318,7 +318,6 @@ static void __exit dm_exit(void)
 	/*
 	 * Should be empty by this point.
 	 */
-	idr_remove_all(&_minor_idr);
 	idr_destroy(&_minor_idr);
 }