Added `CONFIG_SKALD_ADV_CHANNELS` which is then parsed to
and ordered list `SKALD_ADV_CHAN`
Co-authored-by: Leandro Lanzieri <leandro.lanzieri@haw-hamburg.de>
Skald is a very small and simple, TX-only BLE stack that supports
sending advertisements only. It is useful for building all kinds
of BLE beacons with very minimal memory footprints.