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 <geert@linux-m68k.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20211125152154.162780-1-geert@linux-m68k.org
Signed-off-by: Rob Herring <robh@kernel.org>