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.

The u2phy clock flow like this:
===
      u2phy ________________
           |                |    |-----> UTMI_CLK ---------> | EHCI |
OSC_24M ---|---> PHY_PLL----|----|
           |________^_______|    |-----> 480M_CLK ---|G|---> | USBPHY_480M_SRC| ----> USBPHY_480M for SoC
                    |
                    |
                   GRF
===

Signed-off-by: William wu <wulf@rock-chips.com>
Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>