Add Topping E2x2 ucm support

alsa-project/alsa-ucm-conf pull request #803 was opened from oxiadenine:

The Topping E2x2 is an USB audio interface from Topping Professional.

The audio interface has two Microphone/Line/Instrument inputs (1L, 2R), two Line outputs (1L, 2R) and one headphone output.

The "problem" with this audio interface is that by default it exposes 6 hardware channels and ALSA recognizes it as a 5.1 audio system, so the files `E2x2.conf` and `E2x2-HiFi.conf` are to create convenient and user friendly profiles.

Also, a `SectionVerb.EnableSequence` has been added to the file `E2x2-HiFi.conf` to disable the exposed hardware channels that are not used.

USB identifier: `152a:8752`

[alsa-info.txt](https://github.com/user-attachments/files/29563789/alsa-info.txt)

I tested it in several applications like Firefox, Telegram, Discord etc, and also I recorded audio from Ardour (DAW), and all is working as expected.

Request URL   : https://github.com/alsa-project/alsa-ucm-conf/pull/803
Patch URL     : https://github.com/alsa-project/alsa-ucm-conf/pull/803.patch
Repository URL: https://github.com/alsa-project/alsa-ucm-conf