backend/drm: add wlr_drm_connector_state.conn

Allows one to get back the connector from its state. Avoids having
to pass both structs around as function arguments.

backend/drm/drm.c

@@ -354,6 +354,7 @@ static void drm_connector_state_init(struct wlr_drm_connector_state *state,
 		struct wlr_drm_connector *conn,
 		const struct wlr_output_state *base) {
 	memset(state, 0, sizeof(*state));
+	state->conn = conn;
 	state->base = base;
 	state->modeset = base->allow_artifacts;
 	state->active = (base->committed & WLR_OUTPUT_STATE_ENABLED) ?

include/backend/drm/drm.h

@@ -93,6 +93,7 @@ struct wlr_drm_mode {
 };
 
 struct wlr_drm_connector_state {
+	struct wlr_drm_connector *conn;
 	const struct wlr_output_state *base;
 	bool modeset;
 	bool active;