drm/i915: Start using output_types for DPLL selection

encoder->type is not realiable for DP/HDMI so let's switch the DPLL
selection over to using output_types.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171019133721.11794-4-ville.syrjala@linux.intel.com


Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>