ArmVirtPkg/QemuVirtMemInfoLib: use HOB not PCD to record the memory size

Due to the way we inherited the formerly fixed PCDs to describe the
system memory base and size from ArmPlatformPkg, we ended up with a
MemoryInit PEIM that relies on dynamic PCDs to communicate the size of
system memory between the constructor of one of its library dependencies
and the core module. This is unnecessary, and forces us to incorporate
the PCD PEIM as well, for no good reason. So instead, let's use a HOB.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

ArmVirtPkg/Library/QemuVirtMemInfoLib/QemuVirtMemInfoPeiLibConstructor.c

@@ -6,9 +6,10 @@
 
 **/
 
-#include <Base.h>
+#include <Uefi.h>
+#include <Pi/PiMultiPhase.h>
 #include <Library/DebugLib.h>
-#include <Library/PcdLib.h>
+#include <Library/HobLib.h>
 #include <libfdt.h>
 
 RETURN_STATUS
@@ -17,14 +18,14 @@ QemuVirtMemInfoPeiLibConstructor (
   VOID
   )
 {
-  VOID           *DeviceTreeBase;
-  INT32          Node, Prev;
-  UINT64         NewBase, CurBase;
-  UINT64         NewSize, CurSize;
-  CONST CHAR8    *Type;
-  INT32          Len;
-  CONST UINT64   *RegProp;
-  RETURN_STATUS  PcdStatus;
+  VOID          *DeviceTreeBase;
+  INT32         Node, Prev;
+  UINT64        NewBase, CurBase;
+  UINT64        NewSize, CurSize;
+  CONST CHAR8   *Type;
+  INT32         Len;
+  CONST UINT64  *RegProp;
+  VOID          *Hob;
 
   NewBase = 0;
   NewSize = 0;
@@ -86,8 +87,13 @@ QemuVirtMemInfoPeiLibConstructor (
   // Make sure the start of DRAM matches our expectation
   //
   ASSERT (FixedPcdGet64 (PcdSystemMemoryBase) == NewBase);
-  PcdStatus = PcdSet64S (PcdSystemMemorySize, NewSize);
-  ASSERT_RETURN_ERROR (PcdStatus);
+
+  Hob = BuildGuidDataHob (
+          &gArmVirtSystemMemorySizeGuid,
+          &NewSize,
+          sizeof NewSize
+          );
+  ASSERT (Hob != NULL);
 
   //
   // We need to make sure that the machine we are running on has at least