USB: bcma: support old USB 2.0 controller on Northstar devices

Currently bcma-hcd driver handles 3 different bcma cores:
1) BCMA_CORE_USB20_HOST (0x819)
2) BCMA_CORE_NS_USB20 (0x504)
3) BCMA_CORE_NS_USB30 (0x505)

The first one was introduced years ago and so far was used on MIPS
devices only. All Northstar (ARM) devices were using other two cores
which allowed easy implementation of separated initialization paths.

It seems however Broadcom decided to reuse this old USB 2.0 controller
on some recently introduced cheaper Northstar BCM53573 SoCs. I noticed
this on Tenda AC9 (based on BCM47189B0 belonging to BCM53573 family).

There is no difference in this old controller core identification
between MIPS and ARM devices: they share the same id and revision. We
need different controller initialization procedure however.
To handle this add a check for architecture and implement required
initialization for ARM case.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>