arm64: defconfig: enable XORv2 for Marvell Armada 7K/8K

This commit enables the XORv2 DMA driver, which is used on the ARM64
Marvell Armada 7K and 8K platforms.

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