remove an as cast in prefetch codegen

Author: folkertdev

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -330,7 +330,7 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                     _ => bug!(),
                 };
                 let ptr = args[0].immediate();
-                let locality = fn_args.const_at(1).to_value().valtree.unwrap_leaf().to_u32() as i32;
+                let locality = fn_args.const_at(1).to_value().valtree.unwrap_leaf().to_i32();
                 self.call_intrinsic(
                     "llvm.prefetch",
                     &[self.val_ty(ptr)],