configs: Remove is_atomic_cpu check

configs: Remove is_atomic_cpu check

Commit 224f2d50a9873d054f486d7661d947db76f4cf68 removed all instances
of is_atomic_cpu.

Change-Id: I1101fbdbc16dc5d093ab87d3817308176559a548
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20659
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>