arm64: dts: marvell: enable MSI for PCIe on Armada 7K/8K

This commit adds a reference to the appropriate MSI controller in the
description of the PCIe controllers on Marvel Armada 7K and 8K
platforms.

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