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.