MIPS: BMIPS: Add device tree example for BCM63268

MIPS: BMIPS: Add device tree example for BCM63268

This adds a device tree example for Comtrend VR-3032u, which
also serves as a real example for brcm,bcm6328-leds.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Cc: f.fainelli@gmail.com
Cc: jogo@openwrt.org
Cc: cernekee@gmail.com
Cc: robh@kernel.org
Cc: simon@fire.lp0.eu
Cc: john@phrozen.org
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: devicetree@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13842/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>