drm/i915: Remove now useless comments about the translation values

We used to carry a default HDMI value in entry 9, but this entry got
removed for both HSW and BDW.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>