How to get mixer control index from UCM

[GitHub issues - edited]

alsa-project/alsa-lib issue #248 was edited from Zames-Chang:

I use  Corsair VOID ELITE USB Gaming Headset. However this headset have two same name control
```
$ amixer -c 1 scontrols
Simple mixer control 'Auto Gain Control',0
Simple mixer control 'Headset',0
Simple mixer control 'Headset',1
```
use command to change 'Headset',0 is actually not working. But change 'Headset',1 will work. I want write a UCM to indicate that when seeing this headset, choose the name 'Headset' with index 1 not index 0. 

I have seen [use-case.h](https://github.com/alsa-project/alsa-lib/blob/master/include/use-case.h) recommended names for values, but I don't find a proper name to describe control index.

Is there any suggestion about how to write control index in UCM file?

Issue URL     : https://github.com/alsa-project/alsa-lib/issues/248
Repository URL: https://github.com/alsa-project/alsa-lib