leaudio: Fix initialization of the cis cfg

In case of one directional CIS trash could be sent to the controller

Bug: 222674521
Bug: 150670922
Test: atest --bluetooth_le_audio_test bluetoot_le_audio_client_test
Sponsor:@jpawlowski

Change-Id: I9dab5b1172be73087acee0b1ec674a5ac4cda769