IntelFsp2WrapperPkg: Add header for PlatformMultiPhaseLib.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4092

To comply with coding style rule each library class
should have its own header even if it is just a private child library
instance consumed by parent public library in the same package.

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>

IntelFsp2WrapperPkg/Include/Library/FspWrapperPlatformMultiPhaseLib.h

@@ -0,0 +1,30 @@
+/** @file
+  Provide FSP wrapper Platform MultiPhase handling functions.
+
+  Copyright (c) 2022, Intel Corporation. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef FSP_WRAPPER_PLATFORM_MULTI_PHASE_LIB_H_
+#define FSP_WRAPPER_PLATFORM_MULTI_PHASE_LIB_H_
+
+/**
+  FSP Wrapper Platform MultiPhase Handler
+
+  @param[in] FspHobListPtr        - Pointer to FSP HobList (valid after FSP-M completed)
+  @param[in] ComponentIndex       - FSP Component which executing MultiPhase initialization.
+  @param[in] PhaseIndex           - Indicates current execution phase of FSP MultiPhase initialization.
+
+  @retval EFI_STATUS        Always return EFI_SUCCESS
+
+**/
+VOID
+EFIAPI
+FspWrapperPlatformMultiPhaseHandler (
+  IN OUT VOID  **FspHobListPtr,
+  IN UINT8     ComponentIndex,
+  IN UINT32    PhaseIndex
+  );
+
+#endif //FSP_WRAPPER_PLATFORM_MULTI_PHASE_LIB_H_