dt-bindings: iio: adc: exynos-adc: Fix node name in example

"make dt_binding_check":

Documentation/devicetree/bindings/iio/adc/samsung,exynos-adc.example.dt.yaml: ncp15wb473: $nodename:0: 'ncp15wb473' does not match '^thermistor(.*)?$'
From schema: Documentation/devicetree/bindings/hwmon/ntc-thermistor.yaml

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/iio/adc/samsung,exynos-adc.yaml

···
         samsung,syscon-phandle = <&pmu_system_controller>;
 
         /* NTC thermistor is a hwmon device */
-        ncp15wb473 {
+        thermistor {
             compatible = "murata,ncp15wb473";
             pullup-uv = <1800000>;
             pullup-ohm = <47000>;