Revert "[mlir] IntegerRangeAnalysis: don't loop over splat..." (llvm#115388)

Hitting assertion in IREE
https://github.com/iree-org/iree/actions/runs/11732283897/job/32684201665?pr=19066

```
iree-compile: /__w/iree/iree/third_party/llvm-project/mlir/include/mlir/IR/BuiltinAttributes.h:423: auto mlir::DenseElementsAttr::getValues() const [T = llvm::APInt]: Assertion `succeeded(range) && "element type cannot be iterated"' failed.
```


Reverts llvm#115229

Author: IanWood1

mlir/lib/Dialect/Arith/IR/InferIntRangeInterfaceImpls.cpp

@@ -40,11 +40,6 @@ void arith::ConstantOp::inferResultRanges(ArrayRef<ConstantIntRanges> argRanges,
     setResultRange(getResult(), ConstantIntRanges::constant(value));
     return;
   }
-  if (auto splatAttr = llvm::dyn_cast_or_null<SplatElementsAttr>(getValue())) {
-    setResultRange(getResult(), ConstantIntRanges::constant(
-                                    splatAttr.getSplatValue<APInt>()));
-    return;
-  }
   if (auto arrayCstAttr =
           llvm::dyn_cast_or_null<DenseIntElementsAttr>(getValue())) {
     std::optional<ConstantIntRanges> result;