lantiq: update USB controller initialization

This adds USB initialization fixes for Danube, Amazon SE and xrx300 and
should fix the clock on at least Danube which hopefully closes FS#351.

The xrx200 usb driver now uses more memory for the dwc2 fifos, this was
increased in the chip compared to ar9.

This is based in part on the vendor documentation and the vendor code
base as a reference.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>