drm/mediatek: Use CPU when fail to get cmdq event

Even though cmdq client is created successfully, without the cmdq event,
cmdq could not work correctly, so use CPU when fail to get cmdq event.

Fixes: 60fa8c13 ("drm/mediatek: Move gce event property to mutex device node")
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

drivers/gpu/drm/mediatek/mtk_drm_crtc.c

@@ -831,13 +831,19 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
 			drm_crtc_index(&mtk_crtc->base));
 		mtk_crtc->cmdq_client = NULL;
 	}
+
+	if (mtk_crtc->cmdq_client) {
 		ret = of_property_read_u32_index(priv->mutex_node,
 						 "mediatek,gce-events",
 						 drm_crtc_index(&mtk_crtc->base),
 						 &mtk_crtc->cmdq_event);
-	if (ret)
+		if (ret) {
 			dev_dbg(dev, "mtk_crtc %d failed to get mediatek,gce-events property\n",
 				drm_crtc_index(&mtk_crtc->base));
+			cmdq_mbox_destroy(mtk_crtc->cmdq_client);
+			mtk_crtc->cmdq_client = NULL;
+		}
+	}
 #endif
 	return 0;
 }