doesn't use SELECT_MASK() (looks like a bug but it requires
  some more investigation).

* Split off ide_tf_load() helper from do_rw_taskfile().

* Convert __ide_do_rw_disk() to use ide_tf_load().

There should be no functionality changes caused by this patch.

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