arm64: dts: marvell: add description for the slave CP110 in Armada 8K

The Armada 8K platforms (8020 and 8040) have two CP110 HW blocks: one
master, one slave. So far, only the master CP110 was described. This
commit adds the Device Tree description for the slave CP110, and hooks
it up in the DT description of the Armada 8020 and Armada 8040 SoCs.

The slave CP110 description is somewhat similar to the master CP110
description except for a number of things like register offsets,
interrupt numbers, references to clocks, etc.

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