ARM64: dts: marvell: armada-cp110: Add registers clock for I2C nodes

This extra clock is needed to access the registers of the I2C controller
used on the Armada 7K/8K SoCs.

This follows the changes already made in the binding documentation (as
well as in the driver) in:
commit 1534156e ("i2c: mv64xxx: Fix clock
resource by adding an optional bus clock")

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