mem-ruby: add function to check for stalled msgs of addr

mem-ruby: add function to check for stalled msgs of addr

This patch allows a cache controller to check if there
is any stalled message of a specific address in the
stall_map of an input message buffer.

Change-Id: Id2f9bb98a9201a562f2a8cc371e9bb896ac836af
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28133
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>