mem: introduce bad command error to packet commands

The bad command is used to model a request is sent to target but the
target cannot make it. The bad command error is designed to model AXI
SLVERR.

Change-Id: I8142df36a5ed3e461493796266821a2b30a3415e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/64872
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Earl Ou <shunhsingou@google.com>
2 files changed