ARM: mvebu: prepare set_cpu_coherent() for future extension

This patch prepares the set_cpu_coherent() function in coherency.c to
be extended to support other SoCs than Armada XP. It will be needed on
Armada 38x to re-enable the coherency after exiting from suspend to
RAM.

This preparation simply moves the function further down in coherency.c
so that it can use coherency_type(), and uses that function to only do
the Armada XP specific work if we are on Armada XP.

Signed-off-by: Nadav Haklai <nadavh@marvell.com>
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>