hw/arm: Replace global smp variables with machine smp properties

The global smp variables in arm are replaced with smp machine properties.
The init_cpus() and *_create_rpu() are refactored to pass MachineState.

A local variable of the same name would be introduced in the declaration
phase if it's used widely in the context OR replace it on the spot if it's
only used once. No semantic changes.

Signed-off-by: Like Xu <like.xu@linux.intel.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20190518205428.90532-9-like.xu@linux.intel.com>
[ehabkost: Fix hw/arm/sbsa-ref.c and hw/arm/aspeed.c]
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>