ARM: dts: mvebu: Convert mvebu device tree files to 64 bits

In order to be able to use more than 4GB of RAM when the LPAE is
activated, the dts must be converted in 64 bits.

Only Armada XP is LPAE capable, but as it shares a common dtsi file
with Armada 370, then the common file include the skeleton64. Thanks
to the use of the overload capability of the device tree format,
armada-370 include the 32 bit skeleton and all the armada 370 based
dts can remain the same.

This was heavily based on the work of Lior Amsalem.

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