- Sanitize the handling of the ioctl's and fix a bug on the way in dealing with
   the WIN_SMART command where arguments where exchanged.

 - Finally sanitize ioctl further until it turned out that we could get rid of
   the special request type REQ_DRIVE_CMD entierly. We are now using
   consistently REQ_DRIVE_ACB.

   One hidden code path less again!

 - Realize the ide_end_drive_cmd can be on the REQ_DRIVE_ACB only for ioctl() to
   a disk. Eliminate it's usage from device type driver modules.

 - Remove command member from struct  hd_drive_task_hdr and place it in strcut
   ata_taskfile. It is not common between the normal register file and HOB.

   We will have to introduce some helper functions for particular command types.