[MLIR] `tosa.rescale` op validation incorrectly fails on unsigned integer type

[samvid25]

See godbolt: https://godbolt.org/z/8z6Ycahnv
According to the TOSA Spec (here), unsigned 8 and 16-bit types are allowed in the RESCALE operation. The TOSA dialect docs specify the same as well (here).

[llvmbot]

@llvm/issue-subscribers-mlir

Author: Samvid Dharanikota (samvid25)

See godbolt: https://godbolt.org/z/8z6Ycahnv According to the TOSA Spec ([here](https://www.mlplatform.org/tosa/tosa_spec.html#_integer_behavior)), unsigned 8 and 16-bit types are allowed in the RESCALE operation. The TOSA dialect docs specify the same as well ([here](https://github.com/llvm/llvm-project/blob/76db259080fa134579f31d76fe9ab462f47eca87/mlir/include/mlir/Dialect/Tosa/IR/TosaOps.td#L2360)).

[swote-git]

I've identified the issue and am working on fixing this bug.

The problem appears to be a discrepancy between the TOSA Specification and the actual implementation in TosaOps.td. Looking at lines 2359-2360 in TosaOps.td:

| unsigned 8 to signed 8 | uint8 | int8 | true | false |
| signed 8 to unsigned 8 | int8 | uint8 | false | true |

According to this definition, the RESIZE operation should support these conversions between signed and unsigned integer types, but the current implementation doesn't match this specification.

I'll submit a PR to address this inconsistency and ensure the implementation properly follows the TOSA specification.

[samvid25]

Fixed by #138253.