ide: remove obsoleted "hdx=noautotune" kernel parameter

Remove obsoleted "hdx=noautotune" kernel parameter
(it has been obsoleted since 1 Nov 2004).

Then make ide_hwif_t.autotune a single bit flag
and remove no longer needed IDE_TUNE_* defines.

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