WPS: Do not allow Label and Display config methods to be enabled

It is unclear which PIN is used if both Label and Display config
methods are advertised. Avoid this by not allowing such configuration.

wpa_supplicant/wps_supplicant.c

@@ -861,6 +861,13 @@ int wpas_wps_init(struct wpa_supplicant *wpa_s)
 	wps->dev.serial_number = wpa_s->conf->serial_number;
 	wps->config_methods =
 		wps_config_methods_str2bin(wpa_s->conf->config_methods);
+	if ((wps->config_methods & (WPS_CONFIG_DISPLAY | WPS_CONFIG_LABEL)) ==
+	    (WPS_CONFIG_DISPLAY | WPS_CONFIG_LABEL)) {
+		wpa_printf(MSG_ERROR, "WPS: Both Label and Display config "
+			   "methods are not allowed at the same time");
+		os_free(wps);
+		return -1;
+	}
 	if (wpa_s->conf->device_type &&
 	    wps_dev_type_str2bin(wpa_s->conf->device_type,
 				 wps->dev.pri_dev_type) < 0) {