[llvm] [C API] Fix LLVMGetOrdering/LLVMIsAtomicSingleThread for fence/memory instrs (PR #65228)

[Benji Smith via llvm-commits]

Benjins wrote:

Bumping this in case it was missed: if anyone with merge access would be relevant to review or merge, I can ping them. I tried locally merging this into latest main and the tests still passed, so it should still be good in this state

https://github.com/llvm/llvm-project/pull/65228