ARM: mvebu: use armada-380-xor on Armada 38x and 39x

The Armada 38x and 39x SoC support have an updated XOR hardware block
compared to previous SoCs. These features can be enabled by using the
'armada-380-xor' compatible string, available since commit
6f166312

 ("dmaengine: mv_xor: add support for a38x command in
descriptor mode").

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