drm/i915: Flush the residual parking on emergency shutdown

On unwinding following a critical failure inside GEM init, we also need
to be sure to flush the workers before unloading the module.

Testcase: igt/drv_module_reload/basic-reload-inject
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180710094421.16223-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -5550,6 +5550,8 @@ err_init_hw:
 	WARN_ON(i915_gem_suspend(dev_priv));
 	i915_gem_suspend_late(dev_priv);
 
+	i915_gem_drain_workqueue(dev_priv);
+
 	mutex_lock(&dev_priv->drm.struct_mutex);
 	intel_uc_fini_hw(dev_priv);
 err_uc_init:

drivers/gpu/drm/i915/intel_display.c

@@ -15847,6 +15847,8 @@ void intel_modeset_cleanup(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
 
+	flush_workqueue(dev_priv->modeset_wq);
+
 	flush_work(&dev_priv->atomic_helper.free_work);
 	WARN_ON(!llist_empty(&dev_priv->atomic_helper.free_list));