arm64: dts: marvell: add XOR engine description for Armada 7K/8K CP

This commit adds the Device Tree description for the two XOR engines
found in the CP part of the Armada 7K/8K SoC.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>