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>

drivers/gpu/drm/drm_atomic.c

@@ -1063,7 +1063,7 @@ drm_atomic_add_affected_connectors(struct drm_atomic_state *state,
 	 * Changed connectors are already in @state, so only need to look at the
 	 * current configuration.
 	 */
-	list_for_each_entry(connector, &config->connector_list, head) {
+	drm_for_each_connector(connector, state->dev) {
 		if (connector->state->crtc != crtc)
 			continue;