drm/i915: Pass crtc state to intel_prepare_dp_ddi_buffers()

Eliminate intel_prepare_dp_ddi_buffers()'s reliance on the encoder->type
by passing in the crtc state.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171019133721.11794-3-ville.syrjala@linux.intel.com


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