AP: Allow both WPA passphrase and PSK to be configured

AP: Allow both WPA passphrase and PSK to be configured

Instead of dropping the configured PSK and deriving it based on
passphrase, use the provided PSK as-is and also maintain a copy of
the passphrase since it can be of use later. This allows both values
to be configured without havign to derive the PSK every time the
network is initialized.