dt-bindings: iio: avia-hx711: Fix avdd-supply typo in example

Now that examples are validated against the DT schema, a typo in
avia-hx711 example generates a warning:

Documentation/devicetree/bindings/iio/adc/avia-hx711.example.dt.yaml: weight: 'avdd-supply' is a required property

Fix the typo.

Fixes: 5150ec3fe125 ("avia-hx711.yaml: transform DT binding to YAML")
Cc: Andreas Klinger <[e-mail]>
Cc: Jonathan Cameron <[e-mail]>
Cc: [e-mail]
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml

···
         compatible = "avia,hx711";
         sck-gpios = <&gpio3 10 GPIO_ACTIVE_HIGH>;
         dout-gpios = <&gpio0 7 GPIO_ACTIVE_HIGH>;
-        avdd-suppy = <&avdd>;
+        avdd-supply = <&avdd>;
         clock-frequency = <100000>;
     };