ide-scsi: replace ide_do_drive_cmd with blk_execute_rq_nowait
All the callers of ide_do_drive_cmd() except for ide-scsi use
ide_preempt action argument. This converts ide-scsi to use
blk_execute_rq_nowait instead of ide_do_drive_cmd so that we can
remove the action argument in ide_do_drive_cmd and ide_action_t
typedef.