IVGCVSW-5410 Move ILayerSupport.hpp to backends folder

 * ILayerSupport is a backend interface, and so in order 
   to prevent false positives in ABI Compliance Checker 
   move it to backends folder.
 * Front end users should use ABI stable 
   GetILayerSupportByBackendId which takes 
   advantage of LayerSupportHandle

Signed-off-by: Francis Murtagh <francis.murtagh@arm.com>
Change-Id: Ie119451c5d55f114525dc79b6f3474b2df7e3418
!android-nn-driver:5516
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4f43a41..86dad31 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -135,7 +135,7 @@
     include/armnn/Descriptors.hpp
     include/armnn/DescriptorsFwd.hpp
     include/armnn/Exceptions.hpp
-    include/armnn/ILayerSupport.hpp
+    include/armnn/backends/ILayerSupport.hpp
     include/armnn/ILayerVisitor.hpp
     include/armnn/INetwork.hpp
     include/armnn/IProfiler.hpp