Nhlt plugin and simple plugin interface

[GitHub pull_request - edited]

alsa-project/alsa-utils pull request #129 was edited from juimonen:

Initial something... I need to figure out:

- where to specify which plugins to load/run (nhlt now hard coded)
- where to install the plugins
- how to get the to-be-loaded plugin names and where
- is the "hidden-visibility" gcc flag ok to hide other than .so entrypoint

Request URL   : https://github.com/alsa-project/alsa-utils/pull/129
Patch URL     : https://github.com/alsa-project/alsa-utils/pull/129.patch
Repository URL: https://github.com/alsa-project/alsa-utils