IVGCVSW-1804 : Add Subtraction layer types and placeholders

Change-Id: Ib9a477e5ce590df74ba05fece77258b9204f6523
diff --git a/src/armnn/LayerSupport.cpp b/src/armnn/LayerSupport.cpp
index 7ac054c..59c1c8d 100644
--- a/src/armnn/LayerSupport.cpp
+++ b/src/armnn/LayerSupport.cpp
@@ -151,6 +151,16 @@
     FORWARD_LAYER_SUPPORT_FUNC(compute, IsDivisionSupported, input0, input1, output);
 }
 
+bool IsSubtractionSupported(Compute compute,
+                            const TensorInfo& input0,
+                            const TensorInfo& input1,
+                            const TensorInfo& output,
+                            char* reasonIfUnsupported,
+                            size_t reasonIfUnsupportedMaxLength)
+{
+    FORWARD_LAYER_SUPPORT_FUNC(compute, IsSubtractionSupported, input0, input1, output);
+}
+
 bool IsDepthwiseConvolutionSupported(Compute compute,
                                      const TensorInfo& input,
                                      const TensorInfo& output,