Bluetooth: Tests: Use the correct ad data size

The device privacy test was using the wrong value for the advertising
data.

To fix the error, the test now use the `BT_DATA_BYTES` macro to create
the `bt_data` structure.

Also use `BT_DATA_NAME_COMPLETE` instead of the raw value.

Signed-off-by: Théo Battrel <theo.battrel@nordicsemi.no>