drm: Roll out drm_for_each_connector more

Now that we also grab the connection_mutex and so fixed the race with
atomic modeset we can use the iterator there too.

The other special case is drm_connector_unplug_all which would have a
locking inversion with the sysfs store/show functions if we'd grab the
mode_config.mutex around the unplug. We could just grab
connection_mutex instead, but that's a bit too much a dirty trick for
my taste. Also it's only used by udl, which doesn't do any other kind
of connector hotplugging, so should be race-free. Hence just stick
with a comment for now.

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
diff --git a/drivers/gpu/drm/drm_plane_helper.c b/drivers/gpu/drm/drm_plane_helper.c
index 2f0ed11..7e1cde8 100644
--- a/drivers/gpu/drm/drm_plane_helper.c
+++ b/drivers/gpu/drm/drm_plane_helper.c
@@ -91,13 +91,14 @@
 	 */
 	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
 
-	list_for_each_entry(connector, &dev->mode_config.connector_list, head)
+	drm_for_each_connector(connector, dev) {
 		if (connector->encoder && connector->encoder->crtc == crtc) {
 			if (connector_list != NULL && count < num_connectors)
 				*(connector_list++) = connector;
 
 			count++;
 		}
+	}
 
 	return count;
 }