IntelFsp2WrapperPkg: Check header revision for MultiPhase support.

IntelFsp2WrapperPkg: Check header revision for MultiPhase support.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4119

Earlier version of FSP header may not have MultiPhase fields present in
the FspInfoHeader so the handler should verify header revision before
accessing the MultiPhase fields from the header.

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