Revert "drm/i915: Don't use the HDMI port color range bit on Valleyview"

The PIPECONF color range bit doesn't appear to be effective, on HDMI
outputs at least. The color range bit in the port register works though,
so let's use it.

I have not yet verified whether the PIPECONF bit works on DP outputs.

This reverts commit 83a2af88.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>