dm cache: remove needless request_queue NULL pointer checks

Since commit ff9ea323 ("block, bdi: an active gendisk always has a
request_queue associated with it") the request_queue pointer returned
from bdev_get_queue() shall never be NULL.
Signed-off-by: NXu Wang <vulab@iscas.ac.cn>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

drivers/md/dm-cache-target.c

@@ -3387,7 +3387,7 @@ static bool origin_dev_supports_discard(struct block_device *origin_bdev)
 {
 	struct request_queue *q = bdev_get_queue(origin_bdev);
 
-	return q && blk_queue_discard(q);
+	return blk_queue_discard(q);
 }
 
 /*