net: mvpp2: use {get, put}_cpu() instead of smp_processor_id()

smp_processor_id() should not be used in migration-enabled contexts. We
originally thought it was OK in the specific situation of this driver,
but it was wrong, and calling smp_processor_id() in a migration-enabled
context prints a big fat warning when CONFIG_DEBUG_PREEMPT=y.

Therefore, this commit replaces the smp_processor_id() in
migration-enabled contexts by the appropriate get_cpu/put_cpu sections.

Reported-by: Marc Zyngier <marc.zyngier@arm.com>
Fixes: a786841d ("net: mvpp2: handle register mapping and access for PPv2.2")
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>