IVGCVSW-4483 Removes boost::polymorphic_pointer_downcast

 * replace boost::polymorphic_pointer_downcast by PolymorphicPointerDowncast
 * replaced/removed includes

Signed-off-by: Jan Eilers <jan.eilers@arm.com>
Change-Id: I0ef934a3804cf05e4c38dec6c4ec49c76111a302
diff --git a/src/backends/neon/workloads/NeonSplitterWorkload.cpp b/src/backends/neon/workloads/NeonSplitterWorkload.cpp
index 19fa7c6..de6f137 100644
--- a/src/backends/neon/workloads/NeonSplitterWorkload.cpp
+++ b/src/backends/neon/workloads/NeonSplitterWorkload.cpp
@@ -80,7 +80,7 @@
     std::vector<arm_compute::ITensor *> aclOutputs;
     for (auto output : m_Data.m_Outputs)
     {
-        arm_compute::ITensor& aclOutput  = boost::polymorphic_pointer_downcast<IAclTensorHandle>(output)->GetTensor();
+        arm_compute::ITensor& aclOutput  = PolymorphicPointerDowncast<IAclTensorHandle>(output)->GetTensor();
         aclOutputs.emplace_back(&aclOutput);
     }