ide-cd: convert ide_cd_queue_pc to use blk_execute_rq

This converts ide_cd_queue_pc to use blk_execute_rq, necessitating
changing the ide_cd_queue_pc prototype into a form that doesn't takes
a pointer to request struct. ide_cd_queue_pc works like scsi_execute.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Borislav Petkov <petkovbb@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>