USB-Audio: Steinberg UR22C - fix capture channels for older firmware

alsa-project/alsa-ucm-conf pull request #554 was opened from perexg:

It seems that firmware version 3.20 added 4 capture channels while previous firmware has only 2 capture channels.

Fixes: https://github.com/alsa-project/alsa-ucm-conf/issues/547

Request URL : https://github.com/alsa-project/alsa-ucm-conf/pull/554 Patch URL : https://github.com/alsa-project/alsa-ucm-conf/pull/554.patch Repository URL: https://github.com/alsa-project/alsa-ucm-conf