drm/i915/ddi: Flush encoder power domain ref puts during driver unload

An async-put on an encoder specific power domain (for instance the AUX
PW domain) may be pending when removing the encoder. Make sure any such
async-puts are complete while the corresponding encoder is still in place
since at least AUX power wells require this to do a power well->PHY
lookup.
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210526143729.2563672-1-imre.deak@intel.com

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

@@ -4063,9 +4063,11 @@ static int intel_ddi_compute_config_late(struct intel_encoder *encoder,
 
 static void intel_ddi_encoder_destroy(struct drm_encoder *encoder)
 {
+	struct drm_i915_private *i915 = to_i915(encoder->dev);
 	struct intel_digital_port *dig_port = enc_to_dig_port(to_intel_encoder(encoder));
 
 	intel_dp_encoder_flush_work(encoder);
+	intel_display_power_flush_work(i915);
 
 	drm_encoder_cleanup(encoder);
 	if (dig_port)