ARM: mvebu: add cpuidle support for Armada 38x

ARM: mvebu: add cpuidle support for Armada 38x

Unlike the Armada XP and the Armada 370, this SoC uses a Cortex A9
core. Consequently, the procedure to enter the idle state is
different: interaction with the SCU, not disabling snooping, etc.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1406120453-29291-16-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>