dt-bindings: usb: convert mediatek, mtk-xhci.txt to YAML schema

Convert mediatek,mtk-xhci.txt to YAML schema mediatek,mtk-xhci.yaml

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20201225075258.33352-9-chunfeng.yun@mediatek.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>