scsi/device_handlers: Use the new blk_opf_t type

Improve static type checking by using the new blk_opf_t type for variables
that represent request flags.

Cc: Hannes Reinecke <hare@suse.com>
Cc: Martin Wilck <mwilck@suse.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220714180729.1065367-43-bvanassche@acm.org


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