ARM: Kirkwood: allow to use netxbig DTSI for d2net_v2 DTS

ARM: Kirkwood: allow to use netxbig DTSI for d2net_v2 DTS

The d2 Network v2 board (d2net_v2) shares a lot of hardware
characteristics with the 2Big and 5Big Network v2 boards. This patch
prepares the kirkwood-netxbig.dtsi file in order to allow to include it
from the d2net_v2 DTS file. The DT nodes only relevant for the 2Big and
5Big Network v2 boards are moved into their respective DTS files.

Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lkml.kernel.org/r/1404830545-15581-2-git-send-email-simon.guinot@sequanux.org
Signed-off-by: Jason Cooper <jason@lakedaemon.net>