OvmfPkg: clone SmmCpuPlatformHookLib from UefiCpuPkg

Clone the Null instance of SmmCpuPlatformHookLib from UefiCpuPkg to
OvmfPkg. In this patch, customize the lib instance only with the following
no-op steps:

- Replace Null/NULL references in filenames and comments with Qemu/QEMU
  references.
- Update copyright notices.
- Clean up and rewrap comment blocks.
- Update INF_VERSION to the latest INF spec version (1.29).
- Update FILE_GUID.
- Drop the UNI file.

This patch is best reviewed with:

$ git show --find-copies=43 --find-copies-harder

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1512
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200226221156.29589-4-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

OvmfPkg/OvmfPkgIa32X64.dsc

@@ -900,7 +900,7 @@
   }
   UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf {
     <LibraryClasses>
-      SmmCpuPlatformHookLib|UefiCpuPkg/Library/SmmCpuPlatformHookLibNull/SmmCpuPlatformHookLibNull.inf
+      SmmCpuPlatformHookLib|OvmfPkg/Library/SmmCpuPlatformHookLibQemu/SmmCpuPlatformHookLibQemu.inf
       SmmCpuFeaturesLib|OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.inf
   }