IVGCVSW-6469 Add MirrorPad FrontEnd and Ref Support

 * Added PaddingMode enum to PaddingDescriptor to enable Symmetric and
   Reflect padding.
 * Added Symmetric and Reflect Ref implementation.
 * Added Serializer & Deserializer support.
 * Added unit tests.

Signed-off-by: Matthew Sloyan <matthew.sloyan@arm.com>
Change-Id: I4bed907b31742b32ccefe5e8ca39a6f1e5bd9dee
diff --git a/src/backends/reference/workloads/CMakeLists.txt b/src/backends/reference/workloads/CMakeLists.txt
index 5727291..f212522 100644
--- a/src/backends/reference/workloads/CMakeLists.txt
+++ b/src/backends/reference/workloads/CMakeLists.txt
@@ -52,6 +52,8 @@
     Concatenate.hpp
     Concatenate.cpp
     Minimum.hpp
+    MirrorPad.cpp
+    MirrorPad.hpp
     Pad.cpp
     Pad.hpp
     Pooling2d.cpp