Bluetooth: BAP: Update encrypt_state when BIG synced after bad code

- When encrypt_state in a receive state of the scan delegator is
  BT_BAP_BIG_ENC_STATE_BAD_CODE, make sure that on synchronization
  encrypt_state is updated to BT_BAP_BIG_ENC_STATE_DEC, as this
  implies that a correct code was provided, so that the broadcast
  assistant is not asked for a correct code any longer.

Signed-off-by: Max Emde <mxem@demant.com>