ARM: dts: Turn on USB host vbus on rk3288-evb

There is no phy driver that works on the Rockchip board for either USB
host port yet.  For now just hardcode the vbus signal to be on all the
time which makes both the dwc2 host and the EHCI port work.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>