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/backend.mk b/src/backends/reference/backend.mk
index 8d7f63d..bf5f340 100644
--- a/src/backends/reference/backend.mk
+++ b/src/backends/reference/backend.mk
@@ -32,6 +32,7 @@
         workloads/DetectionPostProcess.cpp \
         workloads/Dequantize.cpp \
         workloads/ElementwiseFunction.cpp \
+        workloads/Fill.cpp \
         workloads/FullyConnected.cpp \
         workloads/Gather.cpp \
         workloads/InstanceNorm.cpp \
@@ -62,6 +63,7 @@
         workloads/RefElementwiseWorkload.cpp \
         workloads/RefElementwiseUnaryWorkload.cpp \
         workloads/RefFakeQuantizationFloat32Workload.cpp \
+        workloads/RefFillWorkload.cpp \
         workloads/RefFloorWorkload.cpp \
         workloads/RefFullyConnectedWorkload.cpp \
         workloads/RefGatherWorkload.cpp \