stats: Fix incorrect name conflict panic with grouped stats

stats: Fix incorrect name conflict panic with grouped stats

Info::setName() performs a sanity check to ensure that the same stat
name isn't used twice. This doesn't work for new-style stats with a
parent group since the name is only unique within the group. Disable
the check for new-style stats since these usually use names generated
from member variable names.

Change-Id: I590abe6040407c6a4fe582c0782a418165ff5588
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20760
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>