The ARM CCI driver seem to be using smp_processor_id() in a
preemptible context, which is likely to make a DEBUG_PREMPT
kernel scream at boot time.

Turn this into a get_cpu()/put_cpu() that extends over the CPU
hotplug registration, making sure that we don't race against
a CPU down operation.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Cc: stable@vger.kernel.org # 4.2+
Signed-off-by: NPawel Moll <pawel.moll@arm.com>