drm/i915: Don't cancel DRRS worker synchronously for flush/invalidate

It's not needed since the worker rechecks that it didn't race. We only
need to cancel synchronously after disabling drrs to make sure the
worker really is gone (e.g. for driver unload). But for normal
operation the stall is just wasted time.
Reported-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Vandana Kannan <vandana.kannan@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_dp.c

@@ -5181,7 +5181,7 @@ void intel_edp_drrs_invalidate(struct drm_device *dev,
 	if (dev_priv->drrs.type == DRRS_NOT_SUPPORTED)
 		return;
 
-	cancel_delayed_work_sync(&dev_priv->drrs.work);
+	cancel_delayed_work(&dev_priv->drrs.work);
 
 	mutex_lock(&dev_priv->drrs.mutex);
 	if (!dev_priv->drrs.dp) {
@@ -5225,7 +5225,7 @@ void intel_edp_drrs_flush(struct drm_device *dev,
 	if (dev_priv->drrs.type == DRRS_NOT_SUPPORTED)
 		return;
 
-	cancel_delayed_work_sync(&dev_priv->drrs.work);
+	cancel_delayed_work(&dev_priv->drrs.work);
 
 	mutex_lock(&dev_priv->drrs.mutex);
 	if (!dev_priv->drrs.dp) {