ARM: mvebu: Fix the Aurora L2 cache node with the required cache-unified property

The L2 cache controller on the Armada 370 and Armada XP SoCs is a
unified cache. Moreover, the Aurora cache controller is compatible
with the L2x0 cache controller: the "cache-unified" property is
required by its binding.

This patch fixes the Aurora L2 cache node for the Armada 370 and
Armada XP SoCs by adding this property.

Reported-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Link: https://lkml.kernel.org/r/1412588276-4514-1-git-send-email-gregory.clement@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>