cpu: convert memtest to new style stats

Change-Id: I91b17dd46fd0f70816159ea14c1c8f498048c696
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/34137
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
2 files changed