Use blk_mq_alloc_disk and blk_cleanup_disk to simplify the gendisk and
request_queue allocation.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210614060343.3965416-3-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>