blk-integrity: convert to struct device_attribute

Upstream commit 76b8c319.

An upcoming patch will register the integrity attributes directly with
the struct device kobject.
For this the attributes have to be implemented in terms of
struct device_attribute.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20230309-kobj_release-gendisk_integrity-v3-2-ceccb4493c46@weissschuh.net


Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>