21b607adbe
Add a new unit attribute to allow for unsigned integer comparison.
Example:
```mlir
scf.for unsigned %iv_32 = %lb_32 to %ub_32 step %step_32 : i32 {
// body
}
```
Discussion:
https://discourse.llvm.org/t/scf-should-scf-for-support-unsigned-comparison/84655