dt-bindings: iio: adc: Add support for MT7981

The temperature sensor in the MT7981 is same as in the MT7986.
Add compatible string for mt7981.

Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250708220405.1072393-2-olek2@wp.pl
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: abajk

Documentation/devicetree/bindings/iio/adc/mediatek,mt2701-auxadc.yaml

@@ -32,6 +32,10 @@ properties:
           - enum:
               - mediatek,mt7623-auxadc
           - const: mediatek,mt2701-auxadc
+      - items:
+          - enum:
+              - mediatek,mt7981-auxadc
+          - const: mediatek,mt7986-auxadc
       - items:
           - enum:
               - mediatek,mt6893-auxadc