MLBEDSW-2637 Utilise new tensor and operator funcs

add_input_tensor, set_output_tensor, create_const_tensor and
create_reshape_tensor have recently been added.
This replaces all found existing instances with these new helper
functions

Signed-off-by: Michael McGeagh <michael.mcgeagh@arm.com>
Change-Id: If33be8dbf237b2087b562b03cdeb51da1f99a786
diff --git a/ethosu/vela/extract_npu_subgraphs.py b/ethosu/vela/extract_npu_subgraphs.py
index 6747ec9..4adddc1 100644
--- a/ethosu/vela/extract_npu_subgraphs.py
+++ b/ethosu/vela/extract_npu_subgraphs.py
@@ -80,9 +80,8 @@
         op_type = "Const"
     op = Operation(op_type, orig_tens.name + "_input")
     op.attrs["npu_block_type"] = NpuBlockType.Default
-    op.outputs = [new_tens]
     op.scheduled_pass = startup_init_ps
-    new_tens.ops = [op]
+    op.set_output_tensor(new_tens)
     startup_init_ps.ops.append(op)
     startup_init_ps.outputs.append(new_tens)