[flang] [llvm] [mlir] [flang][llvm][OpenMP][OpenACC] Add implicit casts to omp.atomic and acc.atomic (PR #131603)

[Tom Eccles via llvm-commits]

tblah wrote:

Nimish I think this should be okay to merge. @clementval and @razvanlupusoru have had a while to see this and respond.

https://github.com/llvm/llvm-project/pull/131603