drm/i915: Fix CRC support for DP port D on CHV

Add the missing CRC control register value for DP port D on CHV.
Untested as I don't have a CHV machine with DP on port D.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[danvet: Add a check to only allow DP D on chv, not vlv.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>