drm/nouveau/dispnv50: fix runtime pm imbalance on error

[ Upstream commit dc455f4c ]

pm_runtime_get_sync() increments the runtime PM usage counter even
the call returns an error code. Thus a pairing decrement is needed
on the error handling path to keep the counter balanced.
Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/gpu/drm/nouveau/dispnv50/disp.c

@@ -909,8 +909,10 @@ nv50_mstc_detect(struct drm_connector *connector, bool force)
 		return connector_status_disconnected;
 
 	ret = pm_runtime_get_sync(connector->dev->dev);
-	if (ret < 0 && ret != -EACCES)
+	if (ret < 0 && ret != -EACCES) {
+		pm_runtime_put_autosuspend(connector->dev->dev);
 		return connector_status_disconnected;
+	}
 
 	conn_status = drm_dp_mst_detect_port(connector, mstc->port->mgr,
 					     mstc->port);