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/MmPciRootBridgeIo.h

@@ -0,0 +1,37 @@
+/** @file
+  MM PCI Root Bridge IO protocol as defined in the PI 1.5 specification.
+
+  This protocol provides PCI I/O and memory access within MM.
+
+  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 _MM_PCI_ROOT_BRIDGE_IO_H_
+#define _MM_PCI_ROOT_BRIDGE_IO_H_
+
+#include <Protocol/PciRootBridgeIo.h>
+
+#define EFI_MM_PCI_ROOT_BRIDGE_IO_PROTOCOL_GUID \
+  { \
+    0x8bc1714d, 0xffcb, 0x41c3, { 0x89, 0xdc, 0x6c, 0x74, 0xd0, 0x6d, 0x98, 0xea } \
+  }
+
+///
+/// This protocol provides the same functionality as the PCI Root Bridge I/O Protocol defined in the
+/// UEFI 2.1 Specifcation, section 13.2, except that the functions for Map() and Unmap() may return
+/// EFI_UNSUPPORTED.
+///
+typedef EFI_PCI_ROOT_BRIDGE_IO_PROTOCOL  EFI_MM_PCI_ROOT_BRIDGE_IO_PROTOCOL;
+
+extern EFI_GUID gEfiMmPciRootBridgeIoProtocolGuid;
+
+#endif
+