[OPENMP][NVPTX]Reduce memory use for globalized vars in

[OPENMP][NVPTX]Reduce memory use for globalized vars in
target/teams/distribute regions.

Previously introduced globalization scheme that uses memory coalescing
scheme may increase memory usage fr the variables that are devlared in
target/teams/distribute contexts. We don't need 32 copies of such
variables, just 1. Patch reduces memory use in this case.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@344273 91177308-0d34-0410-b5e6-96231b3b80d8