mem-ruby: Fixing Topology

mem-ruby: Fixing Topology

The constructor assumes the number of nodes (i.e. controllers) equal to
the number of external nodes.
This is a not necessarily valid for all cases (e.g MESI_Three_Level -
where L0s are directly connected to L1s).
MachineType_base_number(MachineType_NUM) provides the total number of
controllers.

Signed-off-by: Pouya Fotouhi <pfotouhi@ucdavis.edu>
Change-Id: Id906099dc967ec70aa34dedb0b55351031ff242c
Reviewed-on: https://gem5-review.googlesource.com/c/15716
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>