IVGCVSW-3591 Fixed unexpectedly skipped SUB tests

 * A model that has Inputs with different quantized scales is not compliant with 1.1

Signed-off-by: Mike Kelly <mike.kelly@arm.com>
Change-Id: Ifb8277d78f05b5ef017effa879322a08c0efc851
diff --git a/1.2/HalPolicy.hpp b/1.2/HalPolicy.hpp
index 7468313..285a37f 100644
--- a/1.2/HalPolicy.hpp
+++ b/1.2/HalPolicy.hpp
@@ -66,6 +66,8 @@
 
     static bool ConvertSpaceToDepth(const Operation& operation, const Model& model, ConversionData& data);
 
+    static bool ConvertSub(const Operation& operation, const Model& model, ConversionData& data);
+
     static bool ConvertTanH(const Operation& operation, const Model& model, ConversionData& data);
 
     static bool ConvertLstm(const Operation& operation, const Model& model, ConversionData& data);