bluetooth: leaudio: Fix missing set of BIG_Encryption

In the PTS BASS/SR/CP/BV-19-C test case a client executes Set
Broadcast Code operation of Broadcast Audio Scan Control Point
characteristic with Broadcast_Code set to an invalid value.
After syncing to an ISO stream there is an expected failed attempt
to decrypt the stream data, but the host does not set BIG_Encryption
value to the expected value 0x03 (BT_BAP_BIG_ENC_STATE_BAD_CODE).
Add missing BIG_Encryption state into the failing check.

Signed-off-by: Magdalena Kasenberg <magdalena.kasenberg@codecoup.pl>