MinPlatformPkg: Add SetCacheMtrrLib library class.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2314



MinPlatformPkg should contain the library class header (API)
and the NULL library class instance.

Cc: Michael Kubacki <michael.a.kubacki@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Chasel Chiu <chasel.chiu@intel.com>
Reviewed-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
Reviewed-by: Michael Kubacki <michael.a.kubacki@intel.com>