mtip32xx: simplify sysfs setup

Pass the driver specific attributes directly to device_add_disk instead
of manually creating them after the disk registration.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210614060343.3965416-2-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>