MdeModulePkg/SmmLockBox(PEI): Remove an ASSERT in RestoreLockBox()

This commit is out of the scope for BZ-1409. It is a refinement for the
PEI library instance within SmmLockBoxLib.

For the below ASSERT statement within function RestoreLockBox():
  Status = SmmCommunicationPpi->Communicate (
                                  SmmCommunicationPpi,
                                  &CommBuffer[0],
                                  &CommSize
                                  );
  if (Status == EFI_NOT_STARTED) {
    //
    // Pei SMM communication not ready yet, so we access SMRAM directly
    //
    DEBUG ((DEBUG_INFO, "SmmLockBoxPeiLib Communicate - (%r)\n", Status));
    Status = InternalRestoreLockBoxFromSmram (Guid, Buffer, Length);
    LockBoxParameterRestore->Header.ReturnStatus = (UINT64)Status;
    if (Length != NULL) {
      LockBoxParameterRestore->Length = (UINT64)*Length;
    }
  }
  ASSERT_EFI_ERROR (Status);

It is possible for previous codes to return an error status that is
possible for happen. One example is that, when the 'if' statement
'if (Status == EFI_NOT_STARTED) {' is entered, function
InternalRestoreLockBoxFromSmram() is possible to return 'BUFFER_TOO_SMALL'
if the caller of RestoreLockBox() provides a buffer that is too small to
hold the content of LockBox.

Thus, this commit will remove the ASSERT here.

Please note that the current implementation of RestoreLockBox() is
handling the above-mentioned error case properly, so no additional error
handling codes are needed here.

Cc: Jian J Wang <jian.j.wang@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>

MdeModulePkg/Library/SmmLockBoxLib/SmmLockBoxPeiLib.c

@@ -623,7 +623,6 @@ RestoreLockBox (
       LockBoxParameterRestore->Length = (UINT64)*Length;
     }
   }
-  ASSERT_EFI_ERROR (Status);
 
   if (Length != NULL) {
     *Length = (UINTN)LockBoxParameterRestore->Length;