drm/i915/dp: Power down sink before disable pipe/transcoder clock

Disabling pipe/transcoder clock before power down sink could cause
sink lost signal, causing it to trigger a hotplug to notify source
that link signal was lost.

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NJosé Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191202222513.337777-2-jose.souza@intel.com

drivers/gpu/drm/i915/display/intel_ddi.c

@@ -3802,12 +3802,12 @@ static void intel_ddi_post_disable_dp(struct intel_encoder *encoder,
 	enum phy phy = intel_port_to_phy(dev_priv, encoder->port);
 
 	if (!is_mst) {
-		intel_ddi_disable_pipe_clock(old_crtc_state);
 		/*
 		 * Power down sink before disabling the port, otherwise we end
 		 * up getting interrupts from the sink on detecting link loss.
 		 */
 		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_OFF);
+		intel_ddi_disable_pipe_clock(old_crtc_state);
 	}
 
 	intel_disable_ddi_buf(encoder, old_crtc_state);