[X86] Replace undef value in flaky test

D33311 exposes the flakiness in this test. Replacing the undef placed by
bugpoint, makes it more interesting and robust.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304168 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed