drm/radeon: Take all modeset locks for DP MST hotplug

Similar with the i915 take all modeset locks for mst hotplug. This is
needed to make sure radeon holds both mode_config.mutex and
mode_config.connection_mutex when updating the connector_list, which
is the new (interim) locking regime we want for that.
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

drivers/gpu/drm/radeon/radeon_dp_mst.c

@@ -286,9 +286,9 @@ static struct drm_connector *radeon_dp_add_mst_connector(struct drm_dp_mst_topol
 	drm_mode_connector_set_path_property(connector, pathprop);
 	drm_reinit_primary_mode_group(dev);
 
-	mutex_lock(&dev->mode_config.mutex);
+	drm_modeset_lock_all(dev);
 	radeon_fb_add_connector(rdev, connector);
-	mutex_unlock(&dev->mode_config.mutex);
+	drm_modeset_unlock_all(dev);
 
 	drm_connector_register(connector);
 	return connector;
@@ -303,12 +303,12 @@ static void radeon_dp_destroy_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 
 	drm_connector_unregister(connector);
 	/* need to nuke the connector */
-	mutex_lock(&dev->mode_config.mutex);
+	drm_modeset_lock_all(dev);
 	/* dpms off */
 	radeon_fb_remove_connector(rdev, connector);
 
 	drm_connector_cleanup(connector);
-	mutex_unlock(&dev->mode_config.mutex);
+	drm_modeset_unlock_all(dev);
 	drm_reinit_primary_mode_group(dev);