[DP] Tiny fix of dp and update example (#1273)

### What this PR does / why we need it?
Add `max_num_tokens_across_dp` to AscendMetadata to fix dp

This pr fixes the bug introduced by
https://github.com/vllm-project/vllm-ascend/pull/1229, which add an arg
`max_num_tokens_across_dp` when dp_size > 1.

Signed-off-by: MengqingCao <cmq0113@163.com>

tests/multicard/test_data_parallel.py

@@ -1,66 +0,0 @@
-#
-# Copyright (c) 2025 Huawei Technologies Co., Ltd. All Rights Reserved.
-# Copyright 2023 The vLLM team.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-"""
-Compare the outputs of vLLM with and without aclgraph.
-
-Run `pytest tests/multicard/test_data_parallel.py`.
-"""
-
-import os
-
-import pytest
-
-from tests.conftest import VllmRunner
-from tests.model_utils import check_outputs_equal
-
-MODELS = ["Qwen/Qwen2.5-0.5B-Instruct"]
-
-
-@pytest.mark.skipif(os.getenv("VLLM_USE_V1") == "0",
-                    reason="Data parallel only support on v1")
-@pytest.mark.parametrize("model", MODELS)
-@pytest.mark.parametrize("max_tokens", [32])
-def test_data_parallel_correctness(
-    model: str,
-    max_tokens: int,
-) -> None:
-    example_prompts = [
-        "Hello, my name is", "The president of the United States is",
-        "The capital of France is", "The future of AI is"
-    ]
-
-    with VllmRunner(model_name=model,
-                    max_model_len=1024,
-                    max_num_seqs=16,
-                    data_parallel_size=2,
-                    distributed_executor_backend="mp") as vllm_model:
-        vllm_dp_outputs = vllm_model.generate_greedy(example_prompts,
-                                                     max_tokens)
-
-    with VllmRunner(
-            model_name=model,
-            max_model_len=1024,
-            max_num_seqs=16,
-    ) as vllm_model:
-        vllm_outputs = vllm_model.generate_greedy(example_prompts, max_tokens)
-
-    check_outputs_equal(
-        outputs_0_lst=vllm_outputs,
-        outputs_1_lst=vllm_dp_outputs,
-        name_0="vllm_outputs",
-        name_1="vllm_dp_outputs",
-    )