ublk: remove the empty open and release block device operations

No need to define empty versions, they can just be left out.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220721130916.1869719-4-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/ublk_drv.c

@@ -208,19 +208,8 @@ static inline int ublk_queue_cmd_buf_size(struct ublk_device *ub, int q_id)
 			PAGE_SIZE);
 }
 
-static int ublk_open(struct block_device *bdev, fmode_t mode)
-{
-	return 0;
-}
-
-static void ublk_release(struct gendisk *disk, fmode_t mode)
-{
-}
-
 static const struct block_device_operations ub_fops = {
 	.owner =	THIS_MODULE,
-	.open =		ublk_open,
-	.release =	ublk_release,
 };
 
 #define UBLK_MAX_PIN_PAGES	32