ucm2: add support for "Digidesign Mbox 3"

[GitHub pull_request - opened]

alsa-project/alsa-ucm-conf pull request #237 was opened from ManuLinares:

Add ucm2 support for "Digidesign Mbox 3", 
without it, alsa detects as analog-surround4.0, instead of 2 line and 2 spdif in/out.

[alsa-info.txt](https://github.com/alsa-project/alsa-ucm-conf/files/9944813/alsa-info.txt)

Request URL   : https://github.com/alsa-project/alsa-ucm-conf/pull/237
Patch URL     : https://github.com/alsa-project/alsa-ucm-conf/pull/237.patch
Repository URL: https://github.com/alsa-project/alsa-ucm-conf