Use Tosa_I32EnumAttr instead of StringBasedAttr to represent Tosa enumerations.

This PR replaces `StringBasedAttr` with `Tosa_I32EnumAttr` to represent Tosa enumerations as per the specification.
The intent is to make the IR and C++ APIs more type-safe and prevent fragile string comparisons in passes.

Enumerations rewritten are:

- `Tosa_ResizeTypeAttr`
- `Tosa_NanPropagationAttr`
- `Tosa_RoundingTypeAttr`

BREAKING CHANGE:

This commit changes attribute assembly and the C++ API surface for the listed attributes.
Code that previously used `StringAttr` for these fields must now be updated to use the new enum representation.
In `.mlir` files, replace string literals with the enum assembly (e.g. `mode = #tosa.resize_type<BILINEAR>`).
In C++, update call sites to either pass the generated enum (e.g. `::mlir::tosa::RoundingType::SINGLE_ROUND`) into builder overloads or construct the typed attribute with `tosa::RoundingTypeAttr::get(context, /*enum*/)` and pass that.

Change-Id: Ic101ddfc3bef73a08ab2d6f59f54598c8e0dbad8

Author: AnnuCode

mlir/lib/Dialect/Tosa/Transforms/TosaValidation.cpp

@@ -514,8 +514,9 @@ struct TosaValidation : public tosa::impl::TosaValidationBase<TosaValidation> {
             << "failed attribute check: rounding_mode = DOUBLE_ROUND "
             << "requires extension [doubleround]";
         return false;
-      } else if (rescale.getRoundingMode() == RoundingMode::INEXACT_ROUND &&
-                 !targetEnv.allows(Extension::inexactround)) {
+      }
+      if (rescale.getRoundingMode() == RoundingMode::INEXACT_ROUND &&
+          !targetEnv.allows(Extension::inexactround)) {
         op->emitOpError()
             << "failed attribute check: rounding_mode = INEXACT_ROUND "
             << "requires extension [inexactround]";