Remove

* "hdx=serialize"
* "idex=noautotune"
* "idex=autotune"

kernel params, they have been obsoleted for ages.

"idex=serialize", "hdx=noautotune" and "hdx=autotune" are still available
so there is no funcionality loss caused by this patch.

v2:

* fix CONFIG_BLK_DEV_4DRIVES=y build broken by version 1 of the patch
  [ /me wearing brown paper bag ]
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>