[flang] [llvm] [flang][OpenMP] Parase `bind` clause for `loop` direcitve. (PR #113662)

[Krzysztof Parzyszek via llvm-commits]

kparzysz wrote:

The changes LGTM.  Are you planning to add the lowering updates in a separate patch (i.e. emitting a TODO error, or the actual support)?

https://github.com/llvm/llvm-project/pull/113662