arm64: dts: marvell: add clocks for Armada AP806 XOR engines

The XORv2 engines in the AP side of the Armada 7K/8K SoCs are using the
AP MS core clock as input, so this commit adds the appropriate clocks
properties.

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