tests: Added GTests for base/atomicio.cc

Change-Id: I586a06c70f4e7331b4a31208ef7831e8473509c5
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21699
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>
2 files changed