ARM64: dts: marvell: armada-cp110: Add registers clock for USB host nodes

This extra clock is needed to access the registers of the USB host
controller used on Armada 7K/8K SoCs.

This follow the changes already made in the binding documentation (as
well as in the driver): "usb: host: xhci-plat: Fix clock resource by
adding a register clock"

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>