EmbeddedPkg: rename NullDmaLib to CoherentDmaLib

The name NullDmaLib suggests that this library is a placeholder that
only exists to fulfil formal dependencies on the DmaLib library class
without providing an actual implementation. This is not the case, though:
NullDmaLib does implement DmaLib fully, but doing so simply requires very
little effort on a cache coherent platform. So let's rename it to
CoherentDmaLib instead.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

EmbeddedPkg/Library/CoherentDmaLib/CoherentDmaLib.inf

@@ -0,0 +1,33 @@
+#/** @file
+#
+#  Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
+#  Copyright (c) 2017, Linaro, Ltd. 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.
+#
+#**/
+
+[Defines]
+  INF_VERSION                    = 0x00010019
+  BASE_NAME                      = CoherentDmaLib
+  FILE_GUID                      = 0F2A0816-D319-4ee7-A6B8-D58524E4428F
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = DmaLib
+
+[Sources]
+  CoherentDmaLib.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  EmbeddedPkg/EmbeddedPkg.dec
+
+[LibraryClasses]
+  DebugLib
+  MemoryAllocationLib