audio: utils: Add library documentation

Add more documentation to the tiaudioutils library, more
specifically to the doxygen's main page and missing
documentation in Log.h file.

Doxygen 1.8 or later and Dot is required to properly build
the documentation since it relies on Doxygen's Markdown.

Change-Id: I395fed314aeaad8ded0233ab3a94771b7bb34888
Signed-off-by: Misael Lopez Cruz <misael.lopez@ti.com>
5 files changed