sunxi: add USB EHCI driver

The Allwinner aka sunxi SoCs have one or more USB host controllers.
This adds a driver for their EHCI.

Signed-off-by: Roman Byshko <rbyshko@gmail.com>
Acked-by: Marek Vasut <marex@denx.de>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>