IVGCVSW-2711 Add Serializer and Deserializer for Subtraction

Change-Id: I87836b5314c1f791b4df2ca90d239573ca28a2da
Signed-off-by: Conor Kennedy <conor.kennedy@arm.com>
Signed-off-by: Matteo Martincigh <matteo.martincigh@arm.com>
diff --git a/src/armnnSerializer/Serializer.hpp b/src/armnnSerializer/Serializer.hpp
index bbc67d4..b6f5974 100644
--- a/src/armnnSerializer/Serializer.hpp
+++ b/src/armnnSerializer/Serializer.hpp
@@ -146,6 +146,9 @@
     void VisitNormalizationLayer(const armnn::IConnectableLayer* layer,
                                  const armnn::NormalizationDescriptor& normalizationDescriptor,
                                  const char* name = nullptr) override;
+
+    void VisitSubtractionLayer(const armnn::IConnectableLayer* layer,
+                               const char* name = nullptr) override;
 private:
 
     /// Creates the Input Slots and Output Slots and LayerBase for the layer.