[CFGVPrinter] Fix -dot-cfg-only

The refactoring in r281640 made -dot-cfg-only ignore the "-only" part.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321079 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed