Bluetooth: controller: Add whitelist population with privacy

When using privacy, an additional cache of the actual privacy peers is
required to avoid additional processing in the ISR (since some of the
peers in the whitelist will be disabled by the corresponding privacy
settings). Add the cache and populate the actual whitelist just before
advertising, scanning or initiating a connection.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>