drm/i915/ddi: set sink to power down mode on dp disable

Similar to
commit fdbc3b1f639bb2cbfb32c612b2699e0ba373317d
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Tue Nov 12 17:10:13 2013 +0200

    drm/i915/dp: set sink to power down mode on dp disable

but for DDI, where we've never done this.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Tested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_ddi.c

@@ -1158,9 +1158,10 @@ static void intel_ddi_post_disable(struct intel_encoder *intel_encoder)
 	if (wait)
 		intel_wait_ddi_buf_idle(dev_priv, port);
 
-	if (type == INTEL_OUTPUT_EDP) {
+	if (type == INTEL_OUTPUT_DISPLAYPORT || type == INTEL_OUTPUT_EDP) {
 		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
 		ironlake_edp_panel_vdd_on(intel_dp);
+		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_OFF);
 		ironlake_edp_panel_off(intel_dp);
 	}