IntelFsp2Pkg: Add FSP 2.4 MultiPhase interface.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3916

Provide FSP 2.4 MultiPhase interface and scripts
support.

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>

IntelFsp2Pkg/Library/SecFspSecPlatformLibNull/PlatformSecLibNull.c

@@ -28,6 +28,7 @@ FspUpdSignatureCheck (
 
 /**
   This function handles FspMultiPhaseSiInitApi.
+  Starting from FSP 2.4 this function is obsolete and FspMultiPhaseSiInitApiHandlerV2 is the replacement.
 
   @param[in]  ApiIdx           Internal index of the FSP API.
   @param[in]  ApiParam         Parameter of the FSP API.
@@ -42,3 +43,36 @@ FspMultiPhaseSiInitApiHandler (
 {
   return EFI_SUCCESS;
 }
+
+/**
+  FSP MultiPhase Platform Get Number Of Phases Function.
+
+  Allows an FSP binary to dynamically update the number of phases at runtime.
+  For example, UPD settings could negate the need to enter the multi-phase flow
+  in certain scenarios. If this function returns FALSE, the default number of phases
+  provided by PcdMultiPhaseNumberOfPhases will be returned to the bootloader instead.
+
+  @param[in] ApiIdx                  - Internal index of the FSP API.
+  @param[in] NumberOfPhasesSupported - How many phases are supported by current FSP Component.
+
+  @retval  TRUE  - NumberOfPhases are modified by Platform during runtime.
+  @retval  FALSE - The Default build time NumberOfPhases should be used.
+
+**/
+BOOLEAN
+EFIAPI
+FspMultiPhasePlatformGetNumberOfPhases (
+  IN     UINT8   ApiIdx,
+  IN OUT UINT32  *NumberOfPhasesSupported
+  )
+{
+  /* Example for platform runtime controlling
+  if ((ApiIdx == FspMultiPhaseSiInitApiIndex) && (Feature1Enable == FALSE)) {
+    *NumberOfPhasesSupported = 0;
+    return TRUE;
+  }
+  return FALSE
+  */
+
+  return FALSE;
+}