sargo/bonito: set Bluetooth mac on boot

Bluetooth mac needs to be set for Bluetooth to work.

As a workaround I currently use this:

echo $"stdin for btmgmt" | btmgmt -i hci0 public-addr $(hciconfig hci0 | grep -o $"[[:xdigit:]:]\\{11,17\\}")

This needs a real solution that can be added to the repo.