MdePkg: Add new definitions for Management Mode.

In PI 1.5 version, system management mode name(SMM) has been changed
to Management Mode(MM). It impacts the current code which still use
SMM/Smram/SMI keywords. This patch add new definition which use
MM/MmRam/MMI keywords to follow new spec definitions.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdePkg/Include/Protocol/DxeMmReadyToLock.h

@@ -0,0 +1,25 @@
+/** @file
+  DXE MM Ready To Lock protocol introduced in the PI 1.5 specification.
+
+  Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
+  This program and the accompanying materials
+  are licensed and made available under the terms and conditions of the BSD License
+  which accompanies this distribution.  The full text of the license may be found at
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#ifndef _DXE_MM_READY_TO_LOCK_H_
+#define _DXE_MM_READY_TO_LOCK_H_
+
+#define EFI_DXE_MM_READY_TO_LOCK_PROTOCOL_GUID \
+  { \
+    0x60ff8964, 0xe906, 0x41d0, { 0xaf, 0xed, 0xf2, 0x41, 0xe9, 0x74, 0xe0, 0x8e } \
+  }
+
+extern EFI_GUID gEfiDxeMmReadyToLockProtocolGuid;
+
+#endif