[llvm] [CodeGen][TII] Simplify analyzeSelect (PR #175828)

[Ryan Buchner via llvm-commits]

bababuck wrote:

Is the `Optimizable` argument needed still, or could we just combine it with the return value of `analyzeSelect()`, redefining the return value as `true if select cannot be understood or it is not optimizable`.
```
  if (TII->analyzeSelect(MI, Optimizable))
    return false;
  if (!Optimizable)
    return false;
```
would then just be:
```
  if (TII->analyzeSelect(MI))
    return false;
```

https://github.com/llvm/llvm-project/pull/175828