pc: Refuse CPU hotplug if the resulting APIC ID is too large

The ACPI CPU hotplug code requires APIC IDs to be smaller than
ACPI_CPU_HOTPLUG_ID_LIMIT, so enforce the limit before trying to hotplug
a new vCPU, returning an error instead of crashing.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
