[llvm] [LoopUnroll] Ensure we can accept both `llvm.loop.unroll.full` and `llvm.loop.unroll.enable` metadata on the same loop (NFC) (PR #182381)

[Nikita Popov via llvm-commits]

nikic wrote:

Could you please clarify what the expected semantics of this configuration are? Is it effectively equivalent to only setting `enable`? Or is there some difference from also setting `full`?

https://github.com/llvm/llvm-project/pull/182381