MdeModulePkg: Allow VariablePolicy state to delete protected variables

https://bugzilla.tianocore.org/show_bug.cgi?id=2522

TcgMorLockSmm provides special protections for
the TCG MOR variables. This will check
IsVariablePolicyEnabled() before enforcing
them to allow variable deletion when policy
engine is disabled.

Only allows deletion, not modification.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Bret Barkelew <brbarkel@microsoft.com>
Signed-off-by: Bret Barkelew <brbarkel@microsoft.com>
Reviewed-by: Dandan Bi <dandan.bi@intel.com>
Acked-by: Jian J Wang <jian.j.wang@intel.com>

MdeModulePkg/Universal/Variable/RuntimeDxe/VariableStandaloneMm.inf

@@ -20,6 +20,7 @@
 #
 # Copyright (c) 2010 - 2019, Intel Corporation. All rights reserved.<BR>
 # Copyright (c) 2018, Linaro, Ltd. All rights reserved.<BR>
+# Copyright (c) Microsoft Corporation.
 # SPDX-License-Identifier: BSD-2-Clause-Patent
 #
 ##
@@ -74,6 +75,7 @@
   StandaloneMmDriverEntryPoint
   SynchronizationLib
   VarCheckLib
+  VariablePolicyLib
 
 [Protocols]
   gEfiSmmFirmwareVolumeBlockProtocolGuid        ## CONSUMES