This adds documentation for the gendisk / request_queue refcount
helpers.
Signed-off-by: NLuis Chamberlain <mcgrof@kernel.org>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>