Add profile for Behringer UMC204HD

[GitHub pull_request - opened]

alsa-project/alsa-ucm-conf pull request #128 was opened from brndd:

Adds a profile for the Behringer UMC204HD to split a 4-channel output into two outputs, and a 2-channel input into two inputs, as per the physical layout of the device. I have very little idea what I'm doing, so let me know if something looks incorrect (there's one thing that looks incorrect even to me which I shall point out in a comment below). The config does at least work, though.

[alsa-info.txt](https://github.com/alsa-project/alsa-ucm-conf/files/7698277/alsa-info.txt)


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![UMC204HD_P0BK0_Front_XL](https://user-images.githubusercontent.com/5822375/145704001-5bb9b741-0d1f-4f83-8184-6335c9b53fbf.png)
![UMC204HD_P0BK0_Rear_XL](https://user-images.githubusercontent.com/5822375/145703999-918614e6-3298-4191-a7b6-7260e8eb3638.png)

Request URL   : https://github.com/alsa-project/alsa-ucm-conf/pull/128
Patch URL     : https://github.com/alsa-project/alsa-ucm-conf/pull/128.patch
Repository URL: https://github.com/alsa-project/alsa-ucm-conf