[patch 7/9] get driver from rq->rq_disk->private_data

* add ide_driver_t * to device drivers objects * set it to point at driver's ide_driver_t * store address of this entry in disk->private_data * fix ide_{cd,disk,floppy,tape,scsi}_g accordingly * use rq->rq_disk->private_data instead of drive->driver to obtain driver (this allows us to kill

[patch 7/9] get driver from rq-rq_disk-private_data

* add ide_driver_t * to device drivers objects * set it to point at driver's ide_driver_t * store address of this entry in disk-private_data * fix ide_{cd,disk,floppy,tape,scsi}_g accordingly * use rq-rq_disk-private_data instead of drive-driver to obtain driver (this allows us to kill