[xla:cpu] Add new pthreadpool API to XNN thread pool integration

This is to match the recently added API in pthreadpool.h from
google/pthreadpool@bd09d5c

Otherwise, we would get a linker error when building xnn_threadpool_test:
```
ld: error: undefined symbol: pthreadpool_parallelize_4d_tile_2d_dynamic
```

Command to test:
```
bazel build -c opt --define=pthreadpool_header_only=true \
  //xla/backends/cpu/runtime/xnnpack:xnn_threadpool_test
```

PiperOrigin-RevId: 739193929

Author: penpornk

third_party/xla/xla/backends/cpu/runtime/xnnpack/xnn_threadpool.cc

@@ -41,7 +41,7 @@ limitations under the License.
 //
 // At link time `pthreadpool` symbols resolved to our own implementation. This
 // is a temporary hack around the fact that it's impossible to customize
-// `pthreadpool` implementation at run time. The downsize is that it's
+// `pthreadpool` implementation at run time. The downside is that it's
 // impossible to have two `pthreadpool` implementations linked into the same
 // binary.
 //
@@ -525,6 +525,13 @@ extern "C" void pthreadpool_parallelize_4d_tile_2d_with_uarch(
   LOG(FATAL) << "Not implemented";
 }
 
+extern "C" void pthreadpool_parallelize_4d_tile_2d_dynamic(
+    pthreadpool_t threadpool, pthreadpool_task_4d_tile_2d_dynamic_t function,
+    void* context, size_t range_i, size_t range_j, size_t range_k,
+    size_t range_l, size_t tile_k, size_t tile_l, uint32_t flags) {
+  LOG(FATAL) << "Not implemented";
+}
+
 extern "C" void pthreadpool_parallelize_5d(pthreadpool_t threadpool,
                                            pthreadpool_task_5d_t function,
                                            void* context, size_t range_i,