IntelFsp2Pkg: FSP should support input UPD as NULL.

IntelFsp2Pkg: FSP should support input UPD as NULL.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4114

FSP specification supports input UPD as NULL cases which FSP will
use built-in UPD region instead.
FSP should not return INVALID_PARAMETER in such cases.

In FSP-T entry point case, the valid FSP-T UPD region pointer will be
passed to platform FSP code to consume.
In FSP-M and FSP-S cases, valid UPD pointer will be decided when
updating corresponding pointer field in FspGlobalData.

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>
Reviewed-by: Ted Kuo <ted.kuo@intel.com>