Complete support for "Pro" USB multichannel cards

[GitHub issues - edited]

alsa-project/alsa-ucm-conf issue #154 was edited from perexg:

- [x] channel split using alsa-lib
- [x] channel split inside app
- [ ] channel split hide the specific configs (alsa-lib, app side support)
- [x] mixer control remap using alsa-lib
- [ ] simplify the mixer control remap

Issue URL     : https://github.com/alsa-project/alsa-ucm-conf/issues/154
Repository URL: https://github.com/alsa-project/alsa-ucm-conf