audio.example.xml: Document file attribute for byte controls
audio.example.xml: Document file attribute for byte controls

Change-Id: I89525e615f41b3a72c0466a3a8172aea6802595b
Signed-off-by: Richard Fitzgerald <22ee0097135072451429b5ac45630d52779cd49b@opensource.cirrus.com>

CirrusLogic/tinyhal,CirrusLogic/tinyhal,CirrusLogic/tinyhal