WPS UPnP: Do not update Beacon frames unnecessarily on subscription removal

There is no need to update the WPS IE in Beacon frames when a
subscription is removed if that subscription is not for an actual
selected registrar. For example, this gets rids of unnecessary driver
operations when a subscription request gets rejected when parsing the
callback URLs.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

src/wps/wps_upnp_ap.c

@@ -76,8 +76,10 @@ int upnp_er_set_selected_registrar(struct wps_registrar *reg,
 void upnp_er_remove_notification(struct wps_registrar *reg,
 				 struct subscription *s)
 {
+	bool was_sel_reg = s->selected_registrar;
+
 	s->selected_registrar = 0;
 	eloop_cancel_timeout(upnp_er_set_selected_timeout, s, reg);
-	if (reg)
+	if (reg && was_sel_reg)
 		wps_registrar_selected_registrar_changed(reg, 0);
 }