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/operation.py b/ethosu/vela/operation.py
index adbbff5..0290e81 100644
--- a/ethosu/vela/operation.py
+++ b/ethosu/vela/operation.py
@@ -307,10 +307,9 @@
         return input_tens, outputs, axis, offset_start, offset_end
 
     def set_activation_lut(self, lut_tensor):
-        lut_tensor.consumer_list.append(self)
         self.attrs["fused_activation_function"] = "LUT"
         self.activation_lut = lut_tensor
-        self.inputs.append(lut_tensor)
+        self.add_input_tensor(lut_tensor)
 
     def add_input_tensor(self, tens):
         self.inputs.append(tens)