arm64: dts: marvell: use new binding for the system controller on cp110

The new binding for the system controller on cp110 moved the clock
controller into a subnode. This preliminary step will allow to add gpio
and pinctrl subnodes.

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