MIPS: BCM47XX: Add Luxul devices to the database

MIPS: BCM47XX: Add Luxul devices to the database

So far only Luxul XWR-1750 router was supported. This adds a set of
other Luxul devices based on BCM47XX. It's a standard support for LEDs
and buttons.

Signed-off-by: Dan Haab <dhaab@luxul.com>
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Cc: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15106/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>