aspeed: introduce a configurable number of CPU per machine

aspeed: introduce a configurable number of CPU per machine

The current models of the Aspeed SoCs only have one CPU but future
ones will support SMP. Introduce a new num_cpus field at the SoC class
level to define the number of available CPUs per SoC and also
introduce a 'num-cpus' property to activate the CPUs configured for
the machine.

The max_cpus limit of the machine should depend on the SoC definition
but, unfortunately, these values are not available when the machine
class is initialized. This is the reason why we add a check on
num_cpus in the AspeedSoC realize handler.

SMP support will be activated when models for such SoCs are implemented.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Message-id: 20190618165311.27066-6-clg@kaod.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>