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
Differential Revision: https://reviews.freebsd.org/D28580

(cherry picked from commit cb5f8694a522ab9a80f9f0bd321d8f3ed818dd9b)