mem: Use address range to find the destination port in the xbar

mem: Use address range to find the destination port in the xbar

Previously the xbar used the start address to lookup the port map and
determine the right destination of an incoming packet. This change
uses the full address range to correctly determine the right master.

Change-Id: I5118712c43ae65aba64e71bf030bca5c99770bdd
Reviewed-on: https://gem5-review.googlesource.com/11117
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>