ide: remove CONFIG_BLK_DEV_HD_IDE config option (take 2)

* Remove CONFIG_BLK_DEV_HD hack from init_hwif_default()
  ("hda=noprobe hdb=noprobe" kernel parameters should be used
  instead if somebody wishes to use the old "hd" driver).

* Make CONFIG_BLK_DEV_HD_ONLY config option available also when
  IDE subsystem is used and update help entry.

* Remove no longer needed CONFIG_BLK_DEV_HD_IDE config option.

v2:
* Update documentation to suggest "hda=noprobe hdb=noprobe"
  instead of obsoleted "ide0=noprobe".

* Update Documentation/ide/ide.txt.

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