OvmfPkg: Update PlatformPei to support Tdx guest

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

OvmfPkg/PlatformPei is updated to support Tdx guest. There are below
major changes.
 - Set Tdx related PCDs
 - Publish Tdx RamRegions

In this patch there is another new function BuildPlatformInfoHob ().
This function builds EFI_HOB_PLATFORM_INFO which contains the
HostBridgeDevId. The hob is built in both Td guest and Non-Td guest.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@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/PlatformPei/MemDetect.c

@@ -37,7 +37,6 @@ Module Name:
 
 #include <Library/QemuFwCfgLib.h>
 #include <Library/QemuFwCfgSimpleParserLib.h>
-
 #include "Platform.h"
 
 VOID
@@ -231,7 +230,12 @@ GetPeiMemoryCap (
     PdpEntries  = 1 << (mPlatformInfoHob.PhysMemAddressWidth - 30);
     ASSERT (PdpEntries <= 0x200);
   } else {
-    Pml4Entries = 1 << (mPlatformInfoHob.PhysMemAddressWidth - 39);
+    if (mPlatformInfoHob.PhysMemAddressWidth > 48) {
+      Pml4Entries = 0x200;
+    } else {
+      Pml4Entries = 1 << (mPlatformInfoHob.PhysMemAddressWidth - 39);
+    }
+
     ASSERT (Pml4Entries <= 0x200);
     PdpEntries = 512;
   }
@@ -354,6 +358,11 @@ InitializeRamRegions (
   IN EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
   )
 {
+  if (TdIsEnabled ()) {
+    PlatformTdxPublishRamRegions ();
+    return;
+  }
+
   PlatformQemuInitializeRam (PlatformInfoHob);
 
   SevInitializeRam ();