This adds code to initialize the USB controller and PHY also on Danube,
Amazon SE and AR10. This code is based on the Vendor driver from
different UGW versions and compared to the hardware documentation.

This patch is included in OpenWrt for many years.
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>