ide: use ->data_phase to set ->handler in do_rw_taskfile()

* Use ->data_phase to set ->handler in do_rw_taskfile() instead of
  setting ->handler in callers of ide_raw_taskfile()/do_rw_taskfile().

* Unexport task_no_data_intr() and make it static.

There should be no functionality changes caused by this patch.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>