UefiCpuPkg: Enable Tdx support in MpInitLib

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

In TDVF BSP and APs are simplified. BSP is the vCPU-0, while the others
are treated as APs.

So MP intialization is rather simple. ApWorker is not supported, BSP is
always the working processor, while the APs are just in a
wait-for-precedure state.

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: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>

UefiCpuPkg/Library/MpInitLib/PeiMpInitLib.inf

@@ -24,10 +24,12 @@
 [Sources.IA32]
   Ia32/AmdSev.c
   Ia32/MpFuncs.nasm
+  MpLibTdxNull.c
 
 [Sources.X64]
   X64/AmdSev.c
   X64/MpFuncs.nasm
+  MpLibTdx.c
 
 [Sources.common]
   AmdSev.c
@@ -36,6 +38,7 @@
   MpLib.c
   MpLib.h
   Microcode.c
+  MpIntelTdx.h
 
 [Packages]
   MdePkg/MdePkg.dec