MLBEDSW-1997: POW operator fails to load

 - Dict was returning a str rather than the tuple (str, options)

Change-Id: Ia4359653d05897b2fd123a21c818dc51d831ed79
Signed-off-by: Tim Hall <tim.hall@arm.com>
diff --git a/ethosu/vela/tflite_mapping.py b/ethosu/vela/tflite_mapping.py
index 8e46ef2..c6981aa 100644
--- a/ethosu/vela/tflite_mapping.py
+++ b/ethosu/vela/tflite_mapping.py
@@ -575,7 +575,7 @@
         "Shape",
         OptionsSerializer("ShapeOptions", (("out_type", datatype_deserialize, datatype_serialize),)),
     ),
-    BuiltinOperator.POW: "Pow",
+    BuiltinOperator.POW: ("Pow", None),
     BuiltinOperator.ARG_MIN: (
         "ArgMin",
         OptionsSerializer("ArgMinOptions", (("output_type", datatype_deserialize, datatype_serialize),)),