block: remove unnecessary condition check

kmem_cache_destroy() can handle NULL pointer correctly, so there is
no need to check e->icq_cache before calling kmem_cache_destroy().
Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/elevator.c

@@ -895,8 +895,7 @@ int elv_register(struct elevator_type *e)
 	spin_lock(&elv_list_lock);
 	if (elevator_find(e->elevator_name, e->uses_mq)) {
 		spin_unlock(&elv_list_lock);
-		if (e->icq_cache)
-			kmem_cache_destroy(e->icq_cache);
+		kmem_cache_destroy(e->icq_cache);
 		return -EBUSY;
 	}
 	list_add_tail(&e->list, &elv_list);