blk-ioprio: remove ioprio_blkcg_from_bio()

blk-ioprio: remove ioprio_blkcg_from_bio()

Currently, if config is enabled, then ioprio is always enabled by
default from blkcg_init_disk(), hence there is no point to check if
the policy is enabled from blkg in ioprio_blkcg_from_bio(). Hence remove
it and get blkcg directly from bio.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240719071506.158075-3-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>