dt-binding: usb: add usb-role-switch property

Add a property usb-role-switch to tell the driver that use
USB Role Switch framework to handle the role switch,
it's useful when the driver has already supported other ways,
such as extcon framework etc.

Cc: Biju Das <biju.das@bp.renesas.com>
Cc: Yu Chen <chenyu56@huawei.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/1567070558-29417-2-git-send-email-chunfeng.yun@mediatek.com


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