[llvm] BPF: Ensure __sync_fetch_and_add() always generate atomic_fetch_add insn (PR #101428)

[via llvm-commits]

https://github.com/eddyz87 approved this pull request.

The change itself looks fine to me, have a nitpick regarding dis-assembler behaviour for cpu v3.

https://github.com/llvm/llvm-project/pull/101428