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>
diff --git a/configs/common/CpuConfig.py b/configs/common/CpuConfig.py
index 831287dd..0228148 100644
--- a/configs/common/CpuConfig.py
+++ b/configs/common/CpuConfig.py
@@ -70,7 +70,6 @@
     return tester
 
 is_kvm_cpu = _cpu_subclass_tester("BaseKvmCPU")
-is_atomic_cpu = _cpu_subclass_tester("AtomicSimpleCPU")
 is_noncaching_cpu = _cpu_subclass_tester("NonCachingSimpleCPU")
 
 def get(name):