ide: use do_rw_taskfile() in flagged_taskfile()

Based on the earlier work by Tejun Heo.

* Move setting IDE_TFLAG_LBA48 taskfile flag from do_rw_taskfile()
  function to the callers.

* Add IDE_TFLAG_FLAGGED taskfile flag for flagged taskfiles coming
  from ide_taskfile_ioctl().  Check it instead of ->tf_out_flags.all.

* Add IDE_TFLAG_OUT_DATA taskfile flag to indicate the need to load
  IDE data register in ide_tf_load().

* Add IDE_TFLAG_OUT_* taskfile flags to indicate the need to load
  particular IDE taskfile registers in ide_tf_load().

* Update do_rw_taskfile() and ide_tf_load() users to set respective
  IDE_TFLAG_OUT_* taksfile flags.

* Add task_dma_ok() helper.

* Use IDE_TFLAG_FLAGGED taskfile flag to select HIHI mask in ide_tf_load().

* Use do_rw_taskfile() in flagged_taskfile().

* Remove no longer needed 'tf_out_flags' field from ide_task_t.

There should be no functionality changes caused by this patch.

Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>