powernv: Include NUMA locality information in the CPU topology

ULE uses this topology to try and preserve locality when migrating
threads between CPUs and when performing work stealing. Ensure that on
NUMA systems it will at least take the NUMA topology into account.

Reviewed by: bdragon, jhibbits (previous version)
Tested by: bdragon
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D28580