spapr: remove extra type variable

The sPAPR CPU core typename is already available in the upper
block. Let's use it and move the check upward also.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
