[llvm] [InstCombine] optimize exp(exp(x)) / exp(x) with fast-math (PR #66177)

[Zain Jaffal via llvm-commits]

zjaffal wrote:

I think what we can do is similar to what is done for `exp(x) * exp(y)` by checking for 
```
if (I.isOnlyUserOfAnyOperand())
```
to make sure that `exp(x)` has one user

https://github.com/llvm/llvm-project/pull/66177