Discover CPU topology on multi-die AMD Zen systems

The Nodes per Processor topology information determines how many bits of the
APIC ID represent the Node (Zeppelin die, on Zen systems) ID. Documented in
Ryzen and Epyc Processor Programming Reference (PPR).

Correct topology information enables the scheduler to make better decisions
on this hardware.

Reviewed by: kib@
Tested by: jeff@ (earlier version)
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D11801