IVGCVSW-4386 Add ArmNN reference support for QAsymmS8

 * Added Quantization Scheme for QAsymmS8
 * Added Unit Tests for QAsymmS8
 * Renamed QAsymm8 calls to QAsymmU8

Signed-off-by: Ryan OShea <Ryan.OShea2@arm.com>
Change-Id: I897b4e018ba1d808cc3f8c113f2be2dbad49c8db
diff --git a/src/backends/reference/workloads/Decoders.hpp b/src/backends/reference/workloads/Decoders.hpp
index 6f30978..6a8c756 100644
--- a/src/backends/reference/workloads/Decoders.hpp
+++ b/src/backends/reference/workloads/Decoders.hpp
@@ -81,6 +81,13 @@
                 params.first);
         }
         ARMNN_NO_DEPRECATE_WARN_END
+        case DataType::QAsymmS8:
+        {
+            return std::make_unique<QASymmS8Decoder>(
+                static_cast<const int8_t*>(data),
+                info.GetQuantizationScale(),
+                info.GetQuantizationOffset());
+        }
         case DataType::QAsymmU8:
         {
             return std::make_unique<QASymm8Decoder>(