mem-cache: allow prefetchers to emit page crossing references

mem-cache: allow prefetchers to emit page crossing references

QueuedPrefetcher takes the responsability to check for page
crossing references.

Change-Id: I0ae6bf8be465118990d9ea1cac0da8f70e69aeb1
Reviewed-on: https://gem5-review.googlesource.com/c/14735
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>