IVGCVSW-3992 Add serialization support for ComparisonLayer

* Added serialization support and serialization-deserialization test
  for Comparison
* Added backward compatibility tests for Equal and Greater, to make
  sure they are serialized and deserialized as Comparison
* Refactored serialization tests and reduced code duplication by
  taking advantage of operator==() recently added for Descriptors

Signed-off-by: Aron Virginas-Tar <Aron.Virginas-Tar@arm.com>
Change-Id: Id0fd94ef4b17e4e51c8005e585ea3c47f9c1bd8d
diff --git a/src/armnnSerializer/SerializerUtils.hpp b/src/armnnSerializer/SerializerUtils.hpp
index 578689b..16b83e3 100644
--- a/src/armnnSerializer/SerializerUtils.hpp
+++ b/src/armnnSerializer/SerializerUtils.hpp
@@ -11,6 +11,8 @@
 namespace armnnSerializer
 {
 
+armnnSerializer::ComparisonOperation GetFlatBufferComparisonOperation(armnn::ComparisonOperation comparisonOperation);
+
 armnnSerializer::ConstTensorData GetFlatBufferConstTensorData(armnn::DataType dataType);
 
 armnnSerializer::DataType GetFlatBufferDataType(armnn::DataType dataType);