CTS Failures in Android CpuAcc in Add

* Fusing the activation into Addition is not supported in CpuAcc. Armnn
uses this validate function to decide if fusion is supported.

Resolves COMPMID-4121

Signed-off-by: Teresa Charlin <teresa.charlinreyes@arm.com>
Change-Id: I78cec326057eada32c2bf7d0e8d64a4af5854cd9
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/4911
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Sang-Hoon Park <sang-hoon.park@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
diff --git a/src/runtime/cpu/operators/CpuAdd.cpp b/src/runtime/cpu/operators/CpuAdd.cpp
index 280350f..23b09ac 100644
--- a/src/runtime/cpu/operators/CpuAdd.cpp
+++ b/src/runtime/cpu/operators/CpuAdd.cpp
@@ -39,7 +39,7 @@
 
 Status CpuAdd::validate(const ITensorInfo *src0, const ITensorInfo *src1, const ITensorInfo *dst, ConvertPolicy policy, const ActivationLayerInfo &act_info)
 {
-    ARM_COMPUTE_UNUSED(act_info);
+    ARM_COMPUTE_RETURN_ERROR_ON(act_info.enabled());
     return kernels::CpuAddKernel::validate(src0, src1, dst, policy);
 }
 } // namespace cpu