blk-iolatency: s/blkcg_rq_qos/iolat_rq_qos/

The name was too generic given that there are multiple blkcg rq-qos
policies.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20230413000649.115785-4-tj@kernel.org


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