dt-bindings: phy: Add compatible for Mediatek MT8186

This commit adds dt-binding documentation of T-Phy for Mediatek MT8186 SoC
Platform.
Signed-off-by: Allen-KH Cheng <Allen-KH.Cheng@mediatek.com>
Link: https://lore.kernel.org/r/20220128062050.23978-6-allen-kh.cheng@mediatek.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/phy/mediatek,tphy.yaml

@@ -80,6 +80,7 @@ properties:
               - mediatek,mt2712-tphy
               - mediatek,mt7629-tphy
               - mediatek,mt8183-tphy
+              - mediatek,mt8186-tphy
           - const: mediatek,generic-tphy-v2
       - items:
           - enum: