usb: mtu3: register a USB Role Switch for dual role mode

Because extcon is not allowed for new bindings, and the
dual role switch is supported by USB Role Switch,
especially for Type-C drivers, so register a USB Role
Switch to support the new way

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1567070558-29417-12-git-send-email-chunfeng.yun@mediatek.com


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