Auto merge of #122220 - saethlin:ppc-can-into-atomicptr, r=oli-obk

Only generate a ptrtoint in AtomicPtr codegen when absolutely necessary

This special case was added in this PR: rust-lang/rust#77611 in response to this error message:
```
Intrinsic has incorrect argument type!
void ({}*)* `@llvm.ppc.cfence.p0sl_s`
in function rust_oom
LLVM ERROR: Broken function found, compilation aborted!
[RUSTC-TIMING] std test:false 20.161
error: could not compile `std`
```
But when I tried searching for more information about that intrinsic I found this: llvm/llvm-project#55983 which is a report of someone hitting this same error and a fix was landed in LLVM, 2 years after the above Rust PR.