Add an xsd file for Short Audio Descriptor xml config file.

Please see platform/device/*/files/sadConfigSample.xml as a sample XML.

Test: xmllint --noout --schema hardware/interfaces/tv/cec/1.0/config/sadConfig.xsd  --xinclude device/harman/atom/files/sadConfig.xml
Bug: 80297701
Change-Id: Ic69aff4f480a206f86ef0c345b6d3f7eb87e8c1f
(cherry picked from commit 652af560cd420107b7eb5eac2307e3b53f4294a9)