ide-acpi: cleanup do_drive_set_taskfiles()

* ide_noacpi is already checked by ide_acpi_exec_tfs()
  which is the only user of do_drive_set_taskfiles().

* ide_acpi_exec_tfs() prints sufficient debug info about the
  device so no need to do it again.

* do_drive_get_GTF() + ide_acpi_exec_tfs() make sure that this
  function will never be called with incorrect gtf_length argument
  or if device is not present.

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