[llvm] [mlir] [MLIR][OpenMP] Fix and simplify bounds offset calculation for 1-D GEP offsets (PR #165486)

[Pranav Bhandarkar via llvm-commits]

https://github.com/bhandarkar-pranav approved this pull request.

Thanks for the changes @agozillon. LGTM

https://github.com/llvm/llvm-project/pull/165486