[AArch64] Robustize atomic cmpxchg test a little more. NFC.

We changed the test to test non-constant values in r238049.
We can also use CHECK-NEXT to be a little stricter.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238052 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed