MLBEDSW-10541: Don't connect NPU-only tensors in the output graph
Identify and mark NPU-only tensors as placeholders in the graph_packing step, that way these tensors will be filtered out in the tflite_writer step.
Signed-off-by: Johan Gunnarsson johan.gunnarsson@arm.com Change-Id: I968d6bf050ee27991f5bc59e1075cd03e2bb3229