ARM: mvebu: enable the ARM SCU on Armada 375 and Armada 38x

ARM: mvebu: enable the ARM SCU on Armada 375 and Armada 38x

Contrary to the Armada 370 and XP that used the PJ4B Marvell cores,
the Armada 375 and Armada 38x use the ARM Cortex-A9. A consequence of
this is that the unit responsible for the coherency between CPUs is
now the ARM SCU, and not the Marvell coherency unit (which is still
present to do coherency with I/O devices).

Therefore this commit:

 * Ensures that the selection of the Armada 375 or Armada 38x SoC
   support enables the ARM SCU support in the kernel.

 * Make sure to initialize the SCU at boot time.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1397483228-25625-6-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>