MdeModulePkg/VariableRuntimeDxe: factor out boot service accesses

In preparation of providing a standalone MM based variable runtime
driver, move the existing SMM driver to the new MM services table,
and factor out some pieces that are specific to the traditional
driver, mainly related to the use of UEFI boot services, which are
not accessible to standalone MM drivers.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>

MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.inf

@@ -48,6 +48,7 @@
 [Sources]
   Reclaim.c
   Variable.c
+  VariableTraditionalMm.c
   VariableSmm.c
   VarCheck.c
   Variable.h
@@ -66,7 +67,7 @@
   BaseLib
   SynchronizationLib
   UefiLib
-  SmmServicesTableLib
+  MmServicesTableLib
   BaseMemoryLib
   DebugLib
   DxeServicesTableLib
@@ -85,7 +86,7 @@
   ## PRODUCES
   ## UNDEFINED # SmiHandlerRegister
   gEfiSmmVariableProtocolGuid
-  gEfiSmmEndOfDxeProtocolGuid                   ## NOTIFY
+  gEfiMmEndOfDxeProtocolGuid                    ## NOTIFY
   gEdkiiSmmVarCheckProtocolGuid                 ## PRODUCES
   gEfiTcgProtocolGuid                           ## SOMETIMES_CONSUMES
   gEfiTcg2ProtocolGuid                          ## SOMETIMES_CONSUMES