[llvm] [FPEnv][PowerPC] Correct one more strictfp test. (PR #94793)

[Chen Zheng via llvm-commits]

chenzheng1030 wrote:

> I'm uncertain if llvm.ppc.readflm() is something I need to worry about so I'm opening this review.

`llvm.ppc.readflm()` will not cause any float point exception and it is not a float point instruction as well, so I don't think we should mark it with `strictfp` attribute.

`llvm.ppc.setflm` may cause float point exception for some input, so we need `strictfp` attribute to follow the constraint float point enviroment.

https://github.com/llvm/llvm-project/pull/94793