spi: Add compatible for MT7986

This patch adds dt-binding documentation for MT7986.

Signed-off-by: Leilk Liu <leilk.liu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220315032411.2826-3-leilk.liu@mediatek.com
Signed-off-by: Mark Brown <broonie@kernel.org>

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

@@ -30,6 +30,10 @@ properties:
               - mediatek,mt8192-spi
               - mediatek,mt8195-spi
           - const: mediatek,mt6765-spi
+      - items:
+          - enum:
+              - mediatek,mt7986-spi-ipm
+          - const: mediatek,spi-ipm
       - items:
           - enum:
               - mediatek,mt2701-spi