IntelFsp2Pkg: Support FSP Dispatch mode

IntelFsp2Pkg: Support FSP Dispatch mode

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1241

Add support for both API (original mode) and DISPATCH mode:
1. Add FspMode field from reserved byte of Global
   Data Structure to tell which mode is selected by boot
   loader. If boot loader invoking FSP-M API this field
   will remain as default 0 (API mode), otherwise platform
   FSP should set this field to 1 (Dispatch mode) when
   initializing Global Data Structure.
2. gFspInApiModePpiGuid will be instaled when FSP running in API
   mode and modules only for API mode should have this in depex.
3. If it is DISPATCH mode, FSP will return to PEI dispatcher,
   not directly return to boot loader.
4. DISPATCH mode supports DXE NotifyPhase drivers so FSP
   will not wait for PEI NotifyPhase callbacks, instead it
   will install gFspReadyForNotifyPhasePpiGuid PPI for
   platform to complete late initialization before transferring
   to DXE.

Test: Verified FSP API and DISPATCH modes on 2 internal
      platforms and both boot successfully.

Cc: Jiewen Yao <Jiewen.yao@intel.com>
Cc: Desimone Nathaniel L <nathaniel.l.desimone@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Chasel Chiu <chasel.chiu@intel.com>
Reviewed-by: Jiewen Yao <Jiewen.yao@intel.com>