OvmfPkg: Add PrePiHobListPointerLibTdx

RFC: https://bugzilla.tianocore.org/show_bug.cgi?id=3429

This library sets / gets the Hob list pointer in TDX_WORK_AREA.
This is because it is designed to be used in SEC where the value of
global variable cannot be saved, so the Hob list pointer is saved
in TDX_WORK_AREA.

TDX_WORK_AREA shares the same base address as SEV_WORK_AREA which is
pointed by PcdSevEsWorkAreaBase. This PCD will be renamed to
PcdCcWorkAreaBase as Gerd suggested.
See https://edk2.groups.io/g/devel/message/86642

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>

OvmfPkg/IntelTdx/PrePiHobListPointerLibTdx/PrePiHobListPointerLibTdx.inf

@@ -0,0 +1,29 @@
+#/** @file
+#
+#  Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+#**/
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = PrePiHobListPointerLibTdx
+  FILE_GUID                      = 28297DB9-4CE7-4679-80E6-0270B215A2F2
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = PrePiHobListPointerLib
+
+[Sources]
+  PrePiHobListPointer.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
+  EmbeddedPkg/EmbeddedPkg.dec
+  UefiCpuPkg/UefiCpuPkg.dec
+
+[Pcd]
+  gUefiCpuPkgTokenSpaceGuid.PcdSevEsWorkAreaBase
+
+[LibraryClasses]
+  PcdLib