usb: musb: sunxi: Add support for the Allwinner sunxi musb controller

This is based on initial code to get the Allwinner sunxi musb controller
supported by Chen-Yu Tsai and Roman Byshko.

This adds support for the Allwinner sunxi musb controller in both host only
and otg mode. Peripheral only mode is not supported, as no boards use that.

This has been tested on a cubietruck (A20 SoC) and an UTOO P66 tablet
(A13 SoC) with a variety of devices in host mode and with the g_serial gadget
driver in peripheral mode, plugging otg / host cables in/out a lot of times
in all possible imaginable plug orders.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>