[Polly] LLVM OpenMP Backend -- Fix "static chunked" scheduling.

Static chunked OpenMP scheduling has not been treated correctly.
This patch fixes the problem that threads would not process their
(work-)chunks as intended.

Differential Revision: https://reviews.llvm.org/D61081

GitOrigin-RevId: 1e0be76e9832e3e02262921abac492e9a52382eb
2 files changed