[llvm] [mlir] [llvm][OpenMP] Handle complex types in atomic read (PR #111377)

[Tom Eccles via llvm-commits]

https://github.com/tblah approved this pull request.

Thanks for all the updates.

I still have a few failing tests on my end that I need to minimize and figure out if they are really bugs with the atomic implementation. But I think in the meantime it is better to merge this because it does work for most cases.

https://github.com/llvm/llvm-project/pull/111377