IVGCVSW-8055 Add support for GELU activation function.

* Add support to CpuRef, CpuAcc and GpuAcc
* Add support to tflite parser, classic and opaque tflite delegates
* Add support to serializer and deserializer
* Add Unit tests

Signed-off-by: Teresa Charlin <teresa.charlinreyes@arm.com>
Change-Id: Ibc60ef2ef2a051e6d9af6e15d24c46316ec19de4
diff --git a/src/backends/reference/RefLayerSupport.cpp b/src/backends/reference/RefLayerSupport.cpp
index defdf0d..167639a 100644
--- a/src/backends/reference/RefLayerSupport.cpp
+++ b/src/backends/reference/RefLayerSupport.cpp
@@ -588,6 +588,7 @@
                 case ActivationFunction::Abs:
                 case ActivationFunction::BoundedReLu:
                 case ActivationFunction::Elu:
+                case ActivationFunction::Gelu:
                 case ActivationFunction::HardSwish:
                 case ActivationFunction::LeakyReLu:
                 case ActivationFunction::Linear: