drm: Remove warning from drm_connector_unregister_all()

Commit 6c87e5c ("drm: Rename drm_connector_unplug_all() to
drm_connector_unregister_all()") replaced a manual connectors list walk
in drm_connector_unregister_all() with drm_for_each_connector(). The
list was walked without the mode config mutex locked as that ends up in
a clash with sysfs, but drm_connector_unregister_all() warns when the
mutex isn't locked.

The problem is known and doesn't require a large warning every time
drm_connector_unregister_all() is called. Fix it by reverting to manual
list walk.

Fixes: 6c87e5c ("drm: Rename drm_connector_unplug_all() to drm_connector_unregister_all()")
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1461190874-32674-1-git-send-email-laurent.pinchart+renesas@ideasonboard.com

drivers/gpu/drm/drm_crtc.c

@@ -1122,7 +1122,7 @@ void drm_connector_unregister_all(struct drm_device *dev)
 	struct drm_connector *connector;
 
 	/* FIXME: taking the mode config mutex ends up in a clash with sysfs */
-	drm_for_each_connector(connector, dev)
+	list_for_each_entry(connector, &dev->mode_config.connector_list, head)
 		drm_connector_unregister(connector);
 }
 EXPORT_SYMBOL(drm_connector_unregister_all);