ide: task_error() -> task_error_cmd()

* Move ide_error() call from task_error() to task_pio_intr()
  (the only user).

* Drop no longer used arguments from task_error().

* Rename task_error() to ide_error_cmd().

There should be no functional changes caused by this patch.

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