drm/i915: Cleaning up DDI translation tables

No functional changes.

That state the obvious and just duplicate the place we
need to change whenever the table is updated. So let's clean it.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1452021535-22641-1-git-send-email-rodrigo.vivi@intel.com