arm64: dts: marvell: use ICU for the CP110 slave RTC

When the conversion of the Marvell CP110 Device Tree description from
using GIC interrupts to using ICU interrupts was done, the RTC on the
slave CP110 was left unchanged. This commit fixes that, so that all
devices on the CP properly get their interrupt through the ICU.

Fixes: 6ef84a82

 ("arm64: dts: marvell: enable GICP and ICU on Armada 7K/8K")
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>