ARM: dts: Add a 64 bits version of the skeleton device tree

In order to be able to use more than 4GB address-cells and size-cells
have to be set to 2

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Lior Amsalem <alior@marvell.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>