IVGCVSW-4439: Adding Elu support to Activation

 * Added CpuRef implementation
 * Added Unit Tests
 * Added Quantizer Test
 * Enabled Tests for Neon and CL backends on fp32 only
 * Added to Serializer

Signed-off-by: David Monahan <david.monahan@arm.com>
Change-Id: Ic23e1797dbc9352b40678c389d7fe2b836b582ea
diff --git a/src/backends/reference/RefLayerSupport.cpp b/src/backends/reference/RefLayerSupport.cpp
index 5cb36c4..8f1f170 100644
--- a/src/backends/reference/RefLayerSupport.cpp
+++ b/src/backends/reference/RefLayerSupport.cpp
@@ -108,6 +108,7 @@
             {
                 case ActivationFunction::Abs:
                 case ActivationFunction::BoundedReLu:
+                case ActivationFunction::Elu:
                 case ActivationFunction::LeakyReLu:
                 case ActivationFunction::Linear:
                 case ActivationFunction::ReLu: