IntelFsp2WrapperPkg/FspMeasurementLib: Add header file.

IntelFsp2WrapperPkg/FspMeasurementLib: Add header file.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2376

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Qi Zhang <qi1.zhang@intel.com>
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Message-Id: <20200818062618.3698-3-qi1.zhang@intel.com>
Reviewed-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>