WPS: Drop responses from ER to a STA that is not in WPS protocol

If an ER tries to send a message to a STA that is not in the middle
of WPS protocol, do not try to deliver that. This can help with issues
where an ER takes long time to reply to M1 and another Registrar has
already completed negotiation.

src/ap/wps_hostapd.c

@@ -1188,7 +1188,7 @@ static int hostapd_rx_req_put_wlan_response(
 	}
 #endif /* CONFIG_WPS_STRICT */
 
-	if (!sta) {
+	if (!sta || !(sta->flags & WLAN_STA_WPS)) {
 		wpa_printf(MSG_DEBUG, "WPS UPnP: No matching STA found");
 		return 0;
 	}