ide-pm: always pass 0 error to ide_complete_rq in ide_do_devset

The caller only looks at the scsi_request result field anyway.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Jens Axboe <axboe@fb.com>