arch, base, cpu, dev, mem, sim: Remove #if 0-ed out code.

arch, base, cpu, dev, mem, sim: Remove #if 0-ed out code.

This code will be preserved through version control, but otherwise
creates clutter and will rot in place since it's never compiled.

Change-Id: Id265f6deac445116843956ea5cf1210d8127274e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18608
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>