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/SmmAccessPei.inf

@@ -2,11 +2,10 @@
 # A PEIM with the following responsibilities:
 #
 # - provide SMRAM access by producing PEI_SMM_ACCESS_PPI,
-# - verify & configure the Q35 TSEG in the entry point,
-# - set aside the SMM_S3_RESUME_STATE object at the bottom of TSEG, and expose
-#   it via the gEfiAcpiVariableGuid GUIDed HOB.
+# - verify & configure the Q35 TSEG in the entry point.
 #
 # Copyright (C) 2013, 2015, Red Hat, Inc.
+# Copyright (c) 2024 Intel Corporation.
 #
 # SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -36,9 +35,6 @@
   MdePkg/MdePkg.dec
   OvmfPkg/OvmfPkg.dec
 
-[Guids]
-  gEfiAcpiVariableGuid
-
 [LibraryClasses]
   BaseLib
   BaseMemoryLib
@@ -57,6 +53,9 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35SmramAtDefaultSmbase
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35TsegMbytes
 
+[Guids]
+  gEfiSmmSmramMemoryGuid             # ALWAYS_CONSUMED
+
 [Ppis]
   gPeiSmmAccessPpiGuid           ## PRODUCES