IVGCVSW-1898 : Ref backend folder structure

* Reference backend is renamed to backends/reference as per
  https://confluence.arm.com/display/MLENG/Pluggable+backends

Change-Id: I27a13c274eb60995dfb459e3c49c0e2f60bcd32c
diff --git a/src/backends/test/ArmComputeCl.cpp b/src/backends/test/ArmComputeCl.cpp
index 9a516b6..5ff94c1 100644
--- a/src/backends/test/ArmComputeCl.cpp
+++ b/src/backends/test/ArmComputeCl.cpp
@@ -6,11 +6,11 @@
 #include "test/TensorHelpers.hpp"
 #include "LayerTests.hpp"
 
-#include "backends/CpuTensorHandle.hpp"
-#include "backends/ClWorkloadFactory.hpp"
-#include "backends/ClWorkloads/ClWorkloadUtils.hpp"
-#include "backends/RefWorkloadFactory.hpp"
-#include "backends/ClLayerSupport.hpp"
+#include <backends/CpuTensorHandle.hpp>
+#include <backends/ClWorkloadFactory.hpp>
+#include <backends/ClWorkloads/ClWorkloadUtils.hpp>
+#include <backends/reference/RefWorkloadFactory.hpp>
+#include <backends/ClLayerSupport.hpp>
 #include "ActivationFixture.hpp"
 #include "ClContextControlFixture.hpp"