Bluetooth: BAP: Shell: Add BASS service data to ext-adv

As per the BAP spec, the scan delegator device should add the BASS service
data in the extended advertising data when it requests a broadcast
assistant to scan for it. For testing purposes that's usually the case
with the shell, extended advertising data shall be populated with the
BASS service data.

Signed-off-by: Nithin Ramesh Myliattil <niym@demant.com>