hw/i386: Replace global smp variables with machine smp properties

The global smp variables in i386 are replaced with smp machine properties.
To avoid calling qdev_get_machine() as much as possible, some related funtions
for acpi data generations are refactored. No semantic changes.

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>
Message-Id: <20190518205428.90532-8-like.xu@linux.intel.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>