rk3288 has two kind of usb controller; this adds the ehci variant for
host0 and hsic.

At the moment we don't add any phys for these controllers, but the
default settings seem to work OK.

There is a hardware problem in ohci controller which make it
unavailable and host0 controller can only support high-speed devices.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>