drm/i915/cnl: Don't trust VBT's alternate pin for port D for now.

Cannon Lake's VBT that is currently available for B0 stepping
states that port D uses alternate pin 3 messing up with the
default pin-port mapping table. Using that information we cannot
get HDMI working properly. So for now we don't relly on VBT for
this information.

Cc: Clint Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Clinton Taylor <clinton.a.taylor@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1499375295-6454-1-git-send-email-rodrigo.vivi@intel.com