IVGCVSW-4874 Provide LayerSupportHandle to frontend users

 * Update to use dot operator for IsXXXLayerSupported()
 * Call LayerSupportHandle member funciton to check is Backend Registered

Signed-off-by: Francis Murtagh <francis.murtagh@arm.com>
Change-Id: If0b9876068db8957a8bdb690ad323cd8dce544a4
!armnn:4924
diff --git a/ConversionUtils.hpp b/ConversionUtils.hpp
index c147684..c484f33 100644
--- a/ConversionUtils.hpp
+++ b/ConversionUtils.hpp
@@ -138,11 +138,11 @@
     for (auto&& backendId : backends) \
     { \
         auto layerSupportObject = armnn::GetILayerSupportByBackendId(backendId); \
-        if (layerSupportObject) \
+        if (layerSupportObject.IsBackendRegistered()) \
         { \
             std::string reasonIfUnsupported; \
             supported = \
-                layerSupportObject->func(__VA_ARGS__, armnn::Optional<std::string&>(reasonIfUnsupported)); \
+                layerSupportObject.func(__VA_ARGS__, armnn::Optional<std::string&>(reasonIfUnsupported)); \
             if (supported) \
             { \
                 break; \