[llvm] [PowecPC] Hint branch `bne-` for atomic operation (PR #152529)

[zhijian lin via llvm-commits]

diggerlin wrote:

> A couple potentially silly questions:
> 
> * Does this only concern `PRED_NE`? Should we indicate that in the PR title?
> * How do we determine which `PRED_NE`s we want the hint for, as there are other `PRED_NE`s beyond what is in this PR?
  the PR only concern about the bne- after st*cx instruction.  according to the `power ISA  B.1 Atomic Update Primitives` , it always use the bne- after st*cx.  and according to the comment of the source code , it should be use `bne-` instead of `bne`


https://github.com/llvm/llvm-project/pull/152529