MdePkg: New PCI Express Platform/Override Protocols

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1954

Three interfaces added to PCI Express Platform Protocol:-
(1) GetDevicePolicy() -> to retrieve device-specific platform policies
(2) NotifyDeviceState() -> to notify platform about device PCI Express
    configuration state
(3) GetPolicy() -> to retrieve platform policy about the PCI Express
    feature list
PCI Express Override Protocol is made alias to PCI Express Platform
Protocol.
Following PCI Express features are supported to override by platform
through the new protocols:
1.	Maximum Payload Size (MPS)
2.	Maximum Read Request Size (MRRS)
3.	Extended Tag
4.	Relaxed Ordering
5.	No Snoop
6.	ASPM
7.	Common Clock Configuration
8.	Extended SYNC
9.	Atomic Op
10.	LTR
11.	PTM
12.	Completion Time Out
13.	Clock Power Management
14.	L1 PM Substates

Signed-off-by: Ashraf Javeed <ashraf.javeed@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Ray Ni <ray.ni@intel.com>

MdePkg/Include/Protocol/PciExpressOverride.h

@@ -0,0 +1,37 @@
+/** @file
+  This file declares EFI PCI Express Override protocol which provides the interface between
+  the PCI bus driver/PCI Host Bridge Resource Allocation driver and an implementation's
+  driver to describe the unique features of a platform.
+  This protocol is optional.
+
+Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>
+SPDX-License-Identifier: BSD-2-Clause-Patent
+
+
+**/
+
+#ifndef _PCI_EXPRESS_OVERRIDE_H_
+#define _PCI_EXPRESS_OVERRIDE_H_
+
+///
+/// EFI_PCI_EXPRESS_OVERRIDE_PROTOCOL has the same structure as of EFI_PCI_EXPRESS_PLATFORM_PROTOCOL
+///
+#include "PciExpressPlatform.h"
+
+///
+/// Global ID for the  EFI_PCI_EXPRESS_OVERRIDE_PROTOCOL
+///
+#define EFI_PCI_EXPRESS_OVERRIDE_GUID \
+  { \
+    0xb9d5ea1, 0x66cb, 0x4546, {0xb0, 0xbb, 0x5c, 0x6d, 0xae, 0xd9, 0x42, 0x47} \
+  }
+
+///
+/// Declaration for EFI_PCI_EXPRESS_OVERRIDE_PROTOCOL
+///
+typedef  EFI_PCI_EXPRESS_PLATFORM_PROTOCOL  EFI_PCI_EXPRESS_OVERRIDE_PROTOCOL;
+
+
+extern EFI_GUID   gEfiPciExpressOverrideProtocolGuid;
+
+#endif