USB-Audio: Add support for Solid State Labs SSL 2

alsa-project/alsa-ucm-conf pull request #377 was edited from 999eagle:

This adds support for the [Solid State Labs SSL 2](https://www.solidstatelogic.com/products/ssl2).

Request URL : https://github.com/alsa-project/alsa-ucm-conf/pull/377 Patch URL : https://github.com/alsa-project/alsa-ucm-conf/pull/377.patch Repository URL: https://github.com/alsa-project/alsa-ucm-conf