block: remove the ioprio field from struct request

The request ioprio is only initialized from the first attached bio,
so requests without a bio already never set it.  Directly use the
bio field instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20241112170050.1612998-3-hch@lst.de


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