IVGCVSW-1989 : implement backend creation and registry for Ref,Cl and Neon

!armnn:152557

Change-Id: Ic6b99cddee1597c85de76034d9332fe1bf3aceb1
diff --git a/src/backends/IBackendInternal.hpp b/src/backends/IBackendInternal.hpp
index 1ccf88e..a441abd 100644
--- a/src/backends/IBackendInternal.hpp
+++ b/src/backends/IBackendInternal.hpp
@@ -13,8 +13,8 @@
 class IBackendInternal : public IBackend
 {
 protected:
-    IBackendInternal() {}
-    virtual ~IBackendInternal() {}
+    IBackendInternal() = default;
+    ~IBackendInternal() override = default;
 
 public:
     virtual std::unique_ptr<IWorkloadFactory> CreateWorkloadFactory() const = 0;