ide: move request type specific code from ide_end_drive_cmd() to callers (v3)

* Move request type specific code from ide_end_drive_cmd() to callers.

* Remove stale ide_end_drive_cmd() documentation and drop no longer
  used 'stat' argument.  Then rename the function to ide_complete_rq().

v2:
* Fix handling of blk_pm_request() requests in task_no_data_intr().

v3:
* Some ide_no_data_taskfile() users (HPA code and HDIO_DRIVE_* ioctls
  handlers) access original command later so we need to update it in
  ide_complete_task().

There should be no functional changes caused by this patch.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>