IVGCVSW-4483 Remove boost::polymorphic_downcast

 * exchange boost::polymorphic_downcast with armnn::PolymorphicDowncast
 * remove unnecessary includes of boost::polymorphic_downcast

Signed-off-by: Jan Eilers <jan.eilers@arm.com>
Change-Id: Ie603fb82860fe05fee547dc78073230cc62b2e1f
diff --git a/src/backends/neon/workloads/NeonSpaceToDepthWorkload.cpp b/src/backends/neon/workloads/NeonSpaceToDepthWorkload.cpp
index a4204b2..2982cd1 100644
--- a/src/backends/neon/workloads/NeonSpaceToDepthWorkload.cpp
+++ b/src/backends/neon/workloads/NeonSpaceToDepthWorkload.cpp
@@ -5,6 +5,8 @@
 
 #include "NeonSpaceToDepthWorkload.hpp"
 #include "NeonWorkloadUtils.hpp"
+
+#include <armnn/utility/PolymorphicDowncast.hpp>
 #include <ResolveType.hpp>
 
 namespace armnn
@@ -33,12 +35,12 @@
 
     arm_compute::DataLayout aclDataLayout = ConvertDataLayout(m_Data.m_Parameters.m_DataLayout);
 
-    arm_compute::ITensor& input = boost::polymorphic_downcast<IAclTensorHandle*>(m_Data.m_Inputs[0])->GetTensor();
+    arm_compute::ITensor& input = PolymorphicDowncast<IAclTensorHandle*>(m_Data.m_Inputs[0])->GetTensor();
     input.info()->set_data_layout(aclDataLayout);
 
     int32_t blockSize = boost::numeric_cast<int32_t>(desc.m_Parameters.m_BlockSize);
 
-    arm_compute::ITensor& output = boost::polymorphic_downcast<IAclTensorHandle*>(m_Data.m_Outputs[0])->GetTensor();
+    arm_compute::ITensor& output = PolymorphicDowncast<IAclTensorHandle*>(m_Data.m_Outputs[0])->GetTensor();
     output.info()->set_data_layout(aclDataLayout);
 
     m_Layer.reset(new arm_compute::NESpaceToDepthLayer());