MLCE-82 Add Neon Mean support and unit tests

Factor out new BuildArmComputeReductionCoordinates function
from CL backend into ArmComputeTensorUtils.

Update NEON LayerSupport and WorkloadFactory objects

Change-Id: Icc975ec699199bffafbdb207323df509d35e1e04
diff --git a/src/backends/neon/workloads/CMakeLists.txt b/src/backends/neon/workloads/CMakeLists.txt
index 7b0251c..b7dfc3f 100644
--- a/src/backends/neon/workloads/CMakeLists.txt
+++ b/src/backends/neon/workloads/CMakeLists.txt
@@ -30,6 +30,8 @@
     NeonLstmFloatWorkload.hpp
     NeonMaximumWorkload.cpp
     NeonMaximumWorkload.hpp
+    NeonMeanWorkload.cpp
+    NeonMeanWorkload.hpp
     NeonMergerWorkload.cpp
     NeonMergerWorkload.hpp
     NeonMultiplicationFloatWorkload.cpp