arm64: dts: rockchip: add u2phy clock for ehci and ohci of rk3399
We found that the suspend process was blocked when it run into
ehci/ohci module due to clk-480m of usb2-phy was disabled.
The root cause is that usb2-phy suspended earlier than ehci/ohci
(usb2-phy will be auto suspended if no devices plug-in). and the
clk-480m provided by it was disabled if no module used. However,
some suspend process related ehci/ohci are base on this clock,
so we should refer it into ehci/ohci driver to prevent this case.