IVGCVSW-4620 Add Fill Reference Implementation

 * Add Fill Reference Implementation
 * Refactor FP converter to use static_cast

Signed-off-by: Ryan OShea <Ryan.OShea2@arm.com>
Signed-off-by: Keith Davis <keith.davis@arm.com>
Change-Id: I532e2f982981d047690755fac43a0e9cf8b17dcd
diff --git a/src/backends/reference/RefLayerSupport.hpp b/src/backends/reference/RefLayerSupport.hpp
index eb89946..96bff56 100644
--- a/src/backends/reference/RefLayerSupport.hpp
+++ b/src/backends/reference/RefLayerSupport.hpp
@@ -141,6 +141,11 @@
                                      const FakeQuantizationDescriptor& descriptor,
                                      Optional<std::string&> reasonIfUnsupported = EmptyOptional()) const override;
 
+    bool IsFillSupported(const TensorInfo& input,
+                         const TensorInfo& output,
+                         const FillDescriptor& descriptor,
+                         Optional<std::string&> reasonIfUnsupported = EmptyOptional()) const override;
+
     bool IsFloorSupported(const TensorInfo& input,
                           const TensorInfo& output,
                           Optional<std::string&> reasonIfUnsupported = EmptyOptional()) const override;