* Set taskfile flags for REQ_TYPE_ATA_TASKFILE requests before
  adding the request to the queue.

* Cleanup execute_drive_cmd().

* Remove unnecessary writes to HOB taskfile registers when using
  LBA48 disk for the following cases:

  - Power Management requests
    (WIN_FLUSH_CACHE[_EXT], WIN_STANDBYNOW1, WIN_IDLEIMMEDIATE commands)

  - special commands (WIN_SPECIFY, WIN_RESTORE, WIN_SETMULT)

  - Host Protected Area support (WIN_READ_NATIVE_MAX, WIN_SET_MAX)

  - /proc/ide/ SMART support (WIN_SMART with SMART_ENABLE,
    SMART_READ_VALUES and SMART_READ_THRESHOLDS subcommands)

  - write cache enabling/disabling in ide-disk
    (WIN_SETFEATURES with SETFEATURES_{EN,DIS}_WCACHE)

  - write cache flushing in ide-disk (WIN_FLUSH_CACHE[_EXT])

  - acoustic management in ide-disk
    (WIN_SETFEATURES with SETFEATURES_{EN,DIS}_AAM)

  - door (un)locking in ide-disk (WIN_DOORLOCK, WIN_DOORUNLOCK)

  - /proc/ide/hd?/identify support (WIN_IDENTIFY)

  - ACPI _GTF taskfiles

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