dev,mem,systemc: Implement and use the recvMemBackdoorReq func.

Change-Id: If6e12d4fcef0c31131a9768099a72542a8f62ab1
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/65753
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Gabe Black <gabeblack@google.com>
Reviewed-by: Jui-min Lee <fcrh@google.com>
14 files changed