MIPS: lantiq: Initialize the USB core on boot

There is a DWC2 USB core in these SoCs. To make USB work we need to first
reset and power the state machine. These are SoC specific registers and
not part of the actual USB core.

Signed-off-by: Antti Seppälä <a.seppala@gmail.com>
Signed-off-by: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11449/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>