If MPSK is enabled on any interface, `ssid.mpsk` should be true.
Prevents overwriting true with a false value when multiple interfaces
share the same SSID.
Also allow handling of the 'reload' event even when MPSK is not enabled,
to ensure config reloads are not skipped, e.g. when configuration is empty.
Fixes: WIFI-14484
Signed-off-by: Marek Kwaczynski <marek@shasta.cloud>