dt-bindings: usb: mtk-xhci: add compatible for mt8188

Add compatible for mt8188
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20220707015041.12264-1-chunfeng.yun@mediatek.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml

@@ -31,6 +31,7 @@ properties:
           - mediatek,mt8173-xhci
           - mediatek,mt8183-xhci
           - mediatek,mt8186-xhci
+          - mediatek,mt8188-xhci
           - mediatek,mt8192-xhci
           - mediatek,mt8195-xhci
       - const: mediatek,mtk-xhci