IVGCVSW-3268 Add Reference workload support for the new Prelu Activation layer

 * Added reference workload for the PReLU Activation layer
 * Added factory methods
 * Added validation support
 * Added Int16 support
 * Added unit tests

Change-Id: Ic950d908c5e0a335dccd2960a3ffab0f8b599876
Signed-off-by: Matteo Martincigh <matteo.martincigh@arm.com>
diff --git a/src/backends/reference/backend.mk b/src/backends/reference/backend.mk
index ecd2812..a430f4f 100644
--- a/src/backends/reference/backend.mk
+++ b/src/backends/reference/backend.mk
@@ -25,6 +25,7 @@
         workloads/Concatenate.cpp \
         workloads/Pad.cpp \
         workloads/Pooling2d.cpp \
+        workloads/PreluImpl.cpp \
         workloads/RefActivationWorkload.cpp \
         workloads/RefBatchNormalizationWorkload.cpp \
         workloads/RefBatchToSpaceNdFloat32Workload.cpp \
@@ -50,6 +51,7 @@
         workloads/RefPadWorkload.cpp \
         workloads/RefPermuteWorkload.cpp \
         workloads/RefPooling2dWorkload.cpp \
+        workloads/RefPreluWorkload.cpp \
         workloads/RefQuantizeWorkload.cpp \
         workloads/RefReshapeWorkload.cpp \
         workloads/RefResizeBilinearWorkload.cpp \