EmulatorPkg: Add persistent memory in EmuThunkPpi

The persistent memory is for PEIM to use, and won't lose during cold
or warm reset. PcdPersistentMemorySize is only used by WinHost.c,
other modules can check the persistent memory size using the field
PersistentMemorySize.

Cc: Andrew Fish <afish@apple.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>

EmulatorPkg/Include/Ppi/EmuThunk.h

@@ -2,7 +2,7 @@
   Emulator Thunk to abstract OS services from pure EFI code
 
   Copyright (c) 2008 - 2011, Apple Inc. All rights reserved.<BR>
-
+  Copyright (c) 2022, Intel Corporation. All rights reserved.<BR>
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
@@ -107,6 +107,8 @@ typedef struct {
   EMU_PEI_AUTOSCAN           MemoryAutoScan;
   EMU_PEI_FD_INFORMATION     FirmwareDevices;
   EMU_PEI_THUNK_INTERFACE    Thunk;
+  UINTN                      PersistentMemorySize;
+  UINT8                      PersistentMemory[0];
 } EMU_THUNK_PPI;
 
 extern EFI_GUID  gEmuThunkPpiGuid;