configs: add option for memory channel intlv.

configs: add option for memory channel intlv.

Current memory channel interleave is hard-coded to be maximum between 128
and system's cache line size. Making this value configurable enables use
cases with DMA masters accessing at higher than 128 block granularity.

Change-Id: I8123fa307efd3fd8f16c815ee74a84844bb51edb
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/27629
Tested-by: Gem5 Cloud Project GCB service account <345032938727@cloudbuild.gserviceaccount.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>