ucm: mark internal functions static

alsa-project/alsa-lib pull request #335 was opened from neobrain:

I've ran into build issues in a project that links against both libalsa and libxkbcommon, which both export a function called `parse_string`. Changing internal function to internal linkage (`static`) prevents this kind of problem.

Request URL : https://github.com/alsa-project/alsa-lib/pull/335 Patch URL : https://github.com/alsa-project/alsa-lib/pull/335.patch Repository URL: https://github.com/alsa-project/alsa-lib