PcAtChipsetPkg: INF/DEC file updates to EDK II packages

PcAtChipsetPkg: INF/DEC file updates to EDK II packages

4. PCD information in DEC file comment blocks are either incomplete or incorrect.
This includes detailed description, @Prompt, @ValidRange, @ValidList, @Expression, and [Error.<TokenSpaceGuid>] validation error messages.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qiu, Shumin <shumin.qiu@intel.com>
Reviewed-by: Gao, Liming <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15944 6f19259b-4bc3-4df7-8a09-765794883524