ide: remove 'tf_in_flags' field from ide_task_t

ide: remove 'tf_in_flags' field from ide_task_t

* Add IDE_TFLAG_IN_DATA taskfile flag to indicate the need of reading
  IDE_DATA_REG in ide_end_drive_cmd().

  Set the new flag in ide_taskfile_ioctl() if ->in_flags.b.data is set.

* Add IDE_TFLAG_FLAGGED_SET_IN_FLAGS taskfile flag to indicate the
  need of modifying ->in_flags in ide_taskfile_ioctl().

  Set the new flag in flagged_taskfile() and move the code modifying
  ->tf_in_flags to ide_taskfile_ioctl().

  While at it remove the bogus comment: ->tf_in_flags (except .b.data)
  have no effect on selection of registers to read.

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

As the result we finally have the internals of HDIO_DRIVE_TASKFILE ioctl
separated from the core IDE code.

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>