ARM: mvebu: add Armada 38x support to the coherency code

The Armada 38x has a coherency unit that is similar to the one of the
Armada 375 SoC, except that it does not have the bug of the Armada 375
coherency unit that requires the XOR based workaround.

This commit therefore extends the Marvell EBU coherency code with a
new compatible string to support the Armada 38x coherency unit.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1397483228-25625-9-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>