MdePkg/ArmTrngLib: Add NULL instance of Arm TRNG Library

Bugzilla: 3668 (https://bugzilla.tianocore.org/show_bug.cgi?id=3668)

The Arm True Random Number Generator (TRNG) library defines an
interface to access the entropy source on a platform. On platforms
that do not have access to an entropy source, a NULL instance of
the TRNG library may be useful to satisfy the build dependency.

Therefore, add a NULL instance of the Arm TRNG library.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>

MdePkg/Library/BaseArmTrngLibNull/BaseArmTrngLibNull.inf

@@ -0,0 +1,30 @@
+## @file
+#  Null instance of the Arm TRNG (True Random Number Generator) Library.
+#
+#  Copyright (c) 2021 - 2022, Arm Limited. All rights reserved.<BR>
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 1.29
+  BASE_NAME                      = BaseArmTrngLibNull
+  MODULE_UNI_FILE                = BaseArmTrngLibNull.uni
+  FILE_GUID                      = ABDE1C87-4F50-4B82-9133-7A79E13F69AB
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = ArmTrngLib
+
+#
+#  VALID_ARCHITECTURES           = IA32 X64 ARM AARCH64 RISCV64
+#
+
+[Sources]
+  BaseArmTrngLibNull.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+
+[LibraryClasses]
+  DebugLib