block: provide a request helper for user integrity segments

Provide a helper to keep the request flags and nr_integrity_segments in
sync with the bio's integrity payload. This is an integrity equivalent
to the normal data helper function, 'blk_rq_map_user()'.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20240913182854.2445457-6-kbusch@meta.com


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