mem: Add getAddrRanges in HBMCtrl

This change adds a missed function in HBMCtrl to make
sure that XBar connected to the controller can see
the address ranges covered by both HBM pseudo channels

Change-Id: If88edda42b45a66a6517685e091545a5bba6eab9
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/61469
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/61735
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>