vl.c: Replace smp global variables with smp machine properties

vl.c: Replace smp global variables with smp machine properties

The global smp variables in vl.c are completely replaced with machine properties.

Form this commit, the smp_cpus/smp_cores/smp_threads/max_cpus are deprecated
and only machine properties within MachineState are fully applied and enabled.

Signed-off-by: Like Xu <[email protected]>
Reviewed-by: Alistair Francis <[email protected]>
Message-Id: <20190518205428[email protected]>
Reviewed-by: Eduardo Habkost <[email protected]>
Signed-off-by: Eduardo Habkost <[email protected]>