base-stats,python: Add missing "group" in `_prepare_stats`

Change-Id: Idb25185e1d29ac9fd8c0503d55b56e0568a61d1f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/42704
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
1 file changed