drm/atomic-helper: WARN if fake_commit->hw_done is not completed as expected

For real commits we WARN if ->hw_done hasn't been completed by the time
drm_atomic_helper_commit_cleanup_done() is called. Let's do the same for
the fake commit.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181122143412.11655-2-ville.syrjala@linux.intel.comReviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/drm_atomic_helper.c

@@ -2216,8 +2216,10 @@ void drm_atomic_helper_commit_cleanup_done(struct drm_atomic_state *old_state)
 		spin_unlock(&crtc->commit_lock);
 	}
 
-	if (old_state->fake_commit)
+	if (old_state->fake_commit) {
 		complete_all(&old_state->fake_commit->cleanup_done);
+		WARN_ON(!try_wait_for_completion(&old_state->fake_commit->hw_done));
+	}
 }
 EXPORT_SYMBOL(drm_atomic_helper_commit_cleanup_done);