dt-bindings: clock: rockchip: add USB480M_PHY mux

dt-bindings: clock: rockchip: add USB480M_PHY mux

The USB480M clock can source from a MUX that selects the clock to come
from either of the USB-phy internal 480MHz PLLs. These clocks are
provided by the USB phy driver. This adds the define for it.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240405-clk-rk3568-usb480m-phy-mux-v1-1-6c89de20a6ff@pengutronix.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>