MdePkg: Add the missing spec version information for header files

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: shenglei <shenglei.zhang@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdePkg/Include/Protocol/HiiPopup.h

@@ -2,7 +2,7 @@
   This protocol provides services to display a popup window.
   The protocol is typically produced by the forms browser and consumed by a driver callback handler.
 
-  Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2017-2018, 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 that accompanies this distribution.
   The full text of the license may be found at
@@ -11,6 +11,9 @@
   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 
+  @par Revision Reference:
+  This Protocol was introduced in UEFI Specification 2.7.
+
 **/
 
 #ifndef __HII_POPUP_H__