MEDIUM: cpu-topo: prefer grouping by CCX for "performance" and "efficiency"

MEDIUM: cpu-topo: prefer grouping by CCX for "performance" and "efficiency"

Most of the time, machines made of multiple CPU types use the same L3
for them, and grouping CPUs by frequencies to form groups doesn't bring
any value and on the opposite can impair the incoming connection balancing.
This choice of grouping by cluster was made in order to constitute a good
choice on homogenous machines as well, so better rely on the per-CCX
grouping than the per-cluster one in this case. This will create less
clusters on machines where it counts without affecting other ones.

It doesn't seem necessary to change anything for the "resource" policy
since it selects a single cluster.