dt-bindings: phy: mediatek: tphy: add compatible for mt8188

Add compatible for mt8188

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/20220708065834.25424-1-chunfeng.yun@mediatek.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>