OvmfPkg: Refine SmmAccess implementation

This patch refines the SmmAccess implementation:
1. SmramMap will be retrieved from the
gEfiSmmSmramMemoryGuid instead of original from
the TSEG Memory Base register.
2. Remove the gEfiAcpiVariableGuid creation, thus
the DESCRIPTOR_INDEX definition can be also cleaned.
3. The gEfiAcpiVariableGuid HOB is moved to the
OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
Tested-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>

OvmfPkg/SmmAccess/SmmAccess2Dxe.c

@@ -6,7 +6,7 @@
   driver.
 
   Copyright (C) 2013, 2015, Red Hat, Inc.<BR>
-  Copyright (c) 2009 - 2010, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2009 - 2024, Intel Corporation. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -115,8 +115,6 @@ SmmAccess2DxeGetCapabilities (
   )
 {
   return SmramAccessGetCapabilities (
-           This->LockState,
-           This->OpenState,
            SmramMapSize,
            SmramMap
            );