IntelFsp2Pkg/FspSecCore: Add missing header file in INF file

IntelFsp2Pkg/FspSecCore: Add missing header file in INF file

SecFsp.h is used but missing inf file, which will cause generating
warning message.

Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Signed-off-by: Shenglei Zhang <shenglei.zhang@intel.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Nate DeSimone <nathaniel.l.desimone@intel.com>