MIPS: Netlogic: Add support for USB on XLP2xx

Add USB intialization code to handle the new XLP2XX USB 3.0 block.
This adds xlp/usb-init-xlp2.c to initialize the XLP2XX USB glue-logic
for XHCI and EHCI. Interrupt and IO offset code in xlp-hal/iomap.h
and xlp/nlm_hal.c is also updated for the new USB block.

Signed-off-by: Ganesan Ramalingam <ganesanr@broadcom.com>
Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5744/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>