IVGCVSW-1885 add RefPadWorkload implementation and associated unit tests

 * Added RefPadWorkload implementation
 * Added unit tests and applied them to CL and Ref backends
 * Fixed a bug in ClPadWorkload

Change-Id: I8cb76bc9d60ae8a39b08d40f05d628e3b72f6410
diff --git a/src/backends/reference/backend.mk b/src/backends/reference/backend.mk
index 365faa6..4403ea2 100644
--- a/src/backends/reference/backend.mk
+++ b/src/backends/reference/backend.mk
@@ -17,6 +17,7 @@
         workloads/ConvImpl.cpp \
         workloads/FullyConnected.cpp \
         workloads/Mean.cpp \
+        workloads/Pad.cpp \
         workloads/Pooling2d.cpp \
         workloads/RefActivationFloat32Workload.cpp \
         workloads/RefActivationUint8Workload.cpp \
@@ -43,6 +44,7 @@
         workloads/RefMergerFloat32Workload.cpp \
         workloads/RefMergerUint8Workload.cpp \
         workloads/RefNormalizationFloat32Workload.cpp \
+        workloads/RefPadWorkload.cpp \
         workloads/RefPermuteWorkload.cpp \
         workloads/RefPooling2dFloat32Workload.cpp \
         workloads/RefPooling2dUint8Workload.cpp \