SecurityPkg: Allow VariablePolicy state to delete authenticated variables

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

Causes AuthService to check
IsVariablePolicyEnabled() before enforcing
write protections to allow variable deletion
when policy engine is disabled.

Only allows deletion, not modification.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Chao Zhang <chao.b.zhang@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>

SecurityPkg/Library/AuthVariableLib/AuthVariableLib.inf

@@ -3,6 +3,7 @@
 #
 #  Copyright (c) 2015 - 2016, Intel Corporation. All rights reserved.<BR>
 #  Copyright (c) 2018, ARM Limited. All rights reserved.<BR>
+#  Copyright (c) Microsoft Corporation.
 #
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -41,6 +42,7 @@
   MemoryAllocationLib
   BaseCryptLib
   PlatformSecureLib
+  VariablePolicyLib
 
 [Guids]
   ## CONSUMES            ## Variable:L"SetupMode"