dts: rk3399: move rockchip, vbus-gpio properties into board-specific files

The (shared) rk3399.dtsi had defined the 'rockchip,vbus-gpio'
properties for each USB 3.0 controller.

As the GPIO usage will vary (e.g. one of those GPIOs shuts down one of
the regulators on the RK3399-Q7) between boards, we move this from the
shared dtsi into the device tree file for the EVB board which these
GPIO definitions match.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Simon Glass <sjg@chromium.org>