dt-bindings: soc: rockchip: add rk3588 usb2phy syscon

The usb2phy is accessible via a syscon registers on RK3588, similar
to rk3399.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230403202307.120562-2-sebastian.reichel@collabora.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>