OvmfPkg/SmmCpuFeaturesLib: drop obsolete API implementation

Commit 0426115b67 ("UefiCpuPkg: Remove unused API in
SmmCpuFeaturesLib.h", 2022-12-21) removed the declaration of the function
SmmCpuFeaturesAllocatePageTableMemory() from the "SmmCpuFeaturesLib.h"
library class header.

Remove the API's (null-)implementation from OvmfPkg/SmmCpuFeaturesLib as
well.

Testing: OVMF builds, boots, and suspends/resumes (see earlier in this
series).

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=4235
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c

@@ -1348,34 +1348,3 @@ SmmCpuFeaturesCompleteSmmReadyToLock (
   )
 {
 }
-
-/**
-  This API provides a method for a CPU to allocate a specific region for
-  storing page tables.
-
-  This API can be called more once to allocate memory for page tables.
-
-  Allocates the number of 4KB pages of type EfiRuntimeServicesData and returns
-  a pointer to the allocated buffer.  The buffer returned is aligned on a 4KB
-  boundary.  If Pages is 0, then NULL is returned.  If there is not enough
-  memory remaining to satisfy the request, then NULL is returned.
-
-  This function can also return NULL if there is no preference on where the
-  page tables are allocated in SMRAM.
-
-  @param  Pages                 The number of 4 KB pages to allocate.
-
-  @return A pointer to the allocated buffer for page tables.
-  @retval NULL      Fail to allocate a specific region for storing page tables,
-                    Or there is no preference on where the page tables are
-                    allocated in SMRAM.
-
-**/
-VOID *
-EFIAPI
-SmmCpuFeaturesAllocatePageTableMemory (
-  IN UINTN  Pages
-  )
-{
-  return NULL;
-}