GoXLR: Add 'Broadcast Stream Mix 2' to Capture if channels are available

alsa-project/alsa-ucm-conf pull request #523 was opened from FrostyCoolSlug:

Fixes: #444

Request URL : https://github.com/alsa-project/alsa-ucm-conf/pull/523 Patch URL : https://github.com/alsa-project/alsa-ucm-conf/pull/523.patch Repository URL: https://github.com/alsa-project/alsa-ucm-conf