ARM: kirkwood: DT board setup for Network Space v2 and parents

This patch adds DT board setup for LaCie Network Space v2 and parents,
based on the Marvell Kirkwood 6281 SoC. This includes Network Space v2
(Max) and Internet Space v2.

Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>