dt-bindings: iio: adc: Add compatible for Mediatek MT8186

This commit adds dt-binding documentation of auxadc for Mediatek MT8186 SoC
Platform.
Signed-off-by: Guodong Liu <guodong.liu@mediatek.com>
Acked-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220110084841.575-1-guodong.liu@mediatek.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

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

@@ -34,6 +34,7 @@ properties:
       - items:
           - enum:
               - mediatek,mt8183-auxadc
+              - mediatek,mt8186-auxadc
               - mediatek,mt8195-auxadc
               - mediatek,mt8516-auxadc
           - const: mediatek,mt8173-auxadc