[flang] [llvm] [mlir] [flang][OpenMP] Enable tiling (PR #143715)

[Krzysztof Parzyszek via llvm-commits]

kparzysz wrote:

Let's merge https://github.com/llvm/llvm-project/pull/145917 first.  It's ready to go, and it implements a subset of what this PR does.

https://github.com/llvm/llvm-project/pull/143715