UefiCpuPkg: Add PlatformSecLib

UefiCpuPkg: Add PlatformSecLib

Add PlatformSecLib class and PlatformSecLibNull instance
that is used by the SecCore.  PlatformSecLibNull should
not be used in a platform build.  Instead, it should be
used as a template for implementing a platform specific
instance of the PlatformSecLib library class.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18635 6f19259b-4bc3-4df7-8a09-765794883524