cpu-o3: convert decode to new style stats

Change-Id: Ia67a51f3b2c2d40d8bf09f1636c721550f5e9a23
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33316
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
3 files changed