Bluetooth: controller: Return current ADI when updating aux

When aux is upated, DID is changed and unlike SID it's only stored in
aux PDU. To allow quick access to new DID value, let's just optionally
return current ADI value after aux was updated. It will be useful e.g.
when updating scan response data if we want to put ADI there.

Signed-off-by: Andrzej Kaczmarek <andrzej.kaczmarek@codecoup.pl>