mem: Record the request master ID in the PacketInfo structure.

mem: Record the request master ID in the PacketInfo structure.

That can be recorded in a packet trace.

Change-Id: I3813ab4ea5aadeb40b355ff01f10e8ecab2bb790
Reviewed-on: https://soc-sim-internal-review.googlesource.com/3482
Reviewed-by: Rahul Thakur <rjthakur@google.com>
Reviewed-on: https://gem5-review.googlesource.com/4780
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>