PM: Fix an inverted condition in simplifyFunctionCFG

I mentioned the issue here in code review way back in September and
was sure we'd fixed it, but apparently we forgot:

  http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20150921/301850.html

In any case, as soon as you try to use this pass in anything but the
most basic pipeline everything falls apart. Fix the condition.

llvm-svn: 257935