dt-bindings: arm: add DT binding for Marvell CP110 system controller

This commit adds the DT binding documentation for the Marvell CP110
system controller, which is part of the CP110 HW block, itself used in
the Marvell Armada 7K and 8K SoCs.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Rob Herring <rob@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>