Add return to DIType::Verify

Code scanner ran by Sylvestre Ledru got a no_return bug
in DebugInfo.cpp. Adding the return statements that
should be there.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195772 91177308-0d34-0410-b5e6-96231b3b80d8