Support hidden networks in DSWiFi

`full_ap_demo_debug` sees the network when "Search for APs" is chosen but naturally fails to associate when it's selected, as it doesn't know the SSID. The router does, however, see the attempted association. When "Connect to firmware AP" is chosen and the network is configured in the firmware settings, it prints "Searching", then stops making progress. The router doesn't see any activity.