mem-ruby: more specialized address to node mapping

mem-ruby: more specialized address to node mapping

Added mapAddressToDownstreamMachine that may be used by the protocols
to map an address to different target donwstream controller of the same
type.

These functions do not use the global mapping provided by the network
and map addresses to one of the controllers specified in the
downstream_destinations parameter.

This change facilitates reusing the same cache state-machine/controllers
to model different levels of the cache hierarchy.

Change-Id: I9a202e9461e0d2f16ed232ff8b60bbde2d15570d
Signed-off-by: Tiago Mück <tiago.muck@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/31415
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>