spi: Add compatible for Mediatek MT8186

This commit adds dt-binding documentation of spi bus for Mediatek MT8186 SoC
Platform.
Signed-off-by: Leilk Liu <leilk.liu@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220125012330.13449-4-leilk.liu@mediatek.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/mediatek,spi-mt65xx.yaml

@@ -26,6 +26,7 @@ properties:
       - items:
           - enum:
               - mediatek,mt6779-spi
+              - mediatek,mt8186-spi
               - mediatek,mt8192-spi
               - mediatek,mt8195-spi
           - const: mediatek,mt6765-spi