ARM: dts: Add Goramo MultiLink device tree

This adds a device tree for the Goramo MultiLink IXP425-based
WAN router.

Cc: Krzysztof Hałasa <khalasa@piap.pl>
Cc: openwrt-devel@lists.openwrt.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>