NFC: Rewrite auto castIter -> const auto *castIter

Author: hiraditya

mlir/lib/Dialect/Linalg/IR/LinalgOps.cpp

@@ -3597,7 +3597,7 @@ void MatmulOp::regionBuilder(ImplicitLocOpBuilder &b, Block &block,
   SmallVector<Value> yields;
 
   TypeFn castVal = TypeFn::cast_signed;
-  auto castIter = llvm::find_if(attrs, [&](const NamedAttribute &attr) {
+  const auto *castIter = llvm::find_if(attrs, [&](const NamedAttribute &attr) {
     return attr.getName() == "cast";
   });
   if (castIter != attrs.end()) {