[torchgen] Bump native function max namespace levels due for internal…

… use case (pytorch#97381)

Summary: As titled. Should be trivial

Test Plan: Rely on unit test

Differential Revision: D44314834

Pull Request resolved: pytorch#97381
Approved by: https://github.com/cccclai

torchgen/gen.py

@@ -1452,7 +1452,7 @@ def get_native_function_declarations(
         ns_helper = NamespaceHelper(
             namespace_str=namespace,
             entity_name="",
-            max_level=3,
+            max_level=4,
         )
         # Convert to a set first to remove duplicate kernel names. Backends are
         # allowed to repeat kernel names; only generate the declaration once!