arm64: dts: marvell: describe the PIC and PMU on Armada 7K/8K

This commit adds the necessary Device Tree description for the PIC
interrupt controller and the PMU available in the Marvell Armada 7K and
Armada 8K SoCs.

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