drm/i915: Update Skylake DDI translation table for DP.

When reviewing DDI translation table I noticed few changes we
haven't incorporated yet and it is always good to follow latest
spec.

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/1452009511-15064-1-git-send-email-rodrigo.vivi@intel.com