ide: pass command instead of request to ide_pio_datablock()

* Add IDE_TFLAG_FS taskfile flag and set it for REQ_TYPE_FS requests.

* Convert ->{in,out}put_data methods to take command instead of request
  as an argument.  Then convert pre_task_out_intr(), task_end_request(),
  task_error(), task_in_unexpected(), ide_pio_sector(), ide_pio_multi()
  and ide_pio_datablock() in similar way.

* Rename task_end_request() to ide_finish_cmd().

There should be no functional changes caused by this patch.

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