IVGCVSW-1804 : add subtraction layer to the public interface

Change-Id: I2c1b622b5199000c01af387bb994267c2b91f89c
diff --git a/src/armnn/Network.cpp b/src/armnn/Network.cpp
index 507668a..dc531d1 100644
--- a/src/armnn/Network.cpp
+++ b/src/armnn/Network.cpp
@@ -589,6 +589,11 @@
     return m_Graph->AddLayer<DivisionLayer>(name);
 }
 
+IConnectableLayer* Network::AddSubtractionLayer(const char* name)
+{
+    return m_Graph->AddLayer<SubtractionLayer>(name);
+}
+
 OptimizedNetwork::OptimizedNetwork(std::unique_ptr<Graph> graph)
     : m_Graph(std::move(graph))
 {