MLCE-190: Neon and CL Constant Workloads do not support newer DataTypes

 * Added support for QASYMM8_SIGNED, QSYMM16, QSYMM8 and QSYMM8_PER_CHANNEL to Neon and CL backends
 * Added unit tests to Neon, CL and Ref backends

Signed-off-by: Mike Kelly <mike.kelly@arm.com>
Change-Id: I4c726b6d86b4d75abedd130dcea372d1e82be5c2
diff --git a/src/backends/cl/workloads/ClConstantWorkload.hpp b/src/backends/cl/workloads/ClConstantWorkload.hpp
index 75325dc..e5a1d44 100644
--- a/src/backends/cl/workloads/ClConstantWorkload.hpp
+++ b/src/backends/cl/workloads/ClConstantWorkload.hpp
@@ -5,10 +5,13 @@
 
 #pragma once
 
+#include <arm_compute/core/Error.h>
 #include <backendsCommon/Workload.hpp>
 
 namespace armnn
 {
+arm_compute::Status ClConstantWorkloadValidate(const TensorInfo& output);
+
 class ClConstantWorkload : public BaseWorkload<ConstantQueueDescriptor>
 {
 public: