MIPS: BCM47XX: Prepare support for LEDs

So far this is mostly just a proof of concept, database consists of a
single device. Creating a nice iterateable array wasn't an option
because devices have different amount of LEDs. And we don't want to
waste memory just because of support for a device with dozens on LEDs.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6299/