[llvm] [PowerPC][EarlyIfConversion] Do not insert `isel` if subtarget doesn't support `isel` (PR #72211)

[Nemanja Ivanovic via llvm-commits]

nemanjai wrote:

What problem is this solving? `PPCExpandISEL` should be getting rid of these on targets that don't support them.
I am not against this patch, but there may be other sources of `isel` instructions and if this pass isn't cleaning them up, it may be an indication that something is wrong with that pass.

https://github.com/llvm/llvm-project/pull/72211