[OPENMP] Fixed codegen for firstprivate variables, also marked as lastprivate.

In some rare cases shared copies of lastprivate/firstprivate variables were not updated after the loop directive.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237243 91177308-0d34-0410-b5e6-96231b3b80d8