ArmPlatformPkg: introduce LcdHwLib library class

Add the declaration and include file for the new LcdHwLib library class,
which will allow us to abstract away from platform  variations in the
LCD graphics output driver.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Girish Pathak <girish.pathak@arm.com>
Signed-off-by: Evan Lloyd <evan.lloyd@arm.com>
[ardb: add NULL implementation as well and add it to ArmPlatformPkg.dsc]
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

ArmPlatformPkg/Library/LcdHwNullLib/LcdHwNullLib.inf

@@ -0,0 +1,28 @@
+#/** @file
+#
+#  Copyright (c) 2017, Linaro, Ltd. All rights reserved.
+#
+#  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.
+#
+#**/
+
+[Defines]
+  INF_VERSION                    = 0x0001001A
+  BASE_NAME                      = LcdHwNullLib
+  FILE_GUID                      = bb1fde98-1de2-410e-8850-fdcb8e67ebc0
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = LcdHwLib
+
+[Sources]
+  LcdHwNullLib.c
+
+[Packages]
+  ArmPlatformPkg/ArmPlatformPkg.dec
+  MdePkg/MdePkg.dec