ARM: kirkwood: DT board setup for Network Space Mini v2

This patch adds DT board setup for the LaCie NAS Network Space Mini v2
(aka SafeBox). The hardware characteristics are very close to those of
the Network Space Lite v2. The main difference are:
- A GPIO fan which is only available on the NS2 Mini.
- A single USB host port is wired on the NS2 Mini. The NS2 Lite provides
  an additional dual-mode USB port (host/device).

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