[BugFix][MLA] Fix attn_mask bug for ring mla (#2704)

This PR fix a bug related to attention mask used in ring mla. Current
ring mla has supported compressed mask, so we can directly use a 512 *
512 attention mask.

- vLLM version: v0.10.1.1
- vLLM main:
b5ee1e3261

---------

Signed-off-by: whx-sjtu <2952154980@qq.com>

tests/ut/attention/test_mla_v1.py

@@ -238,13 +238,19 @@ class TestAscendMLAImpl(TestBase):
            new_callable=lambda: MagicMock(spec=GroupCoordinator))
     @patch("vllm.distributed.get_tensor_model_parallel_world_size",
            return_value=2)
-    @patch("vllm.config.get_current_vllm_config")
+    @patch("vllm_ascend.attention.mla_v1.get_current_vllm_config")
     @patch("vllm_ascend.attention.mla_v1.get_ascend_config")
-    def setUp(self, ascend_config, vllm_config, mock_get_tp_size, mock_tp):
+    def setUp(self, ascend_config, get_current_vllm_config, mock_get_tp_size,
+              mock_tp):
         mock_tp.world_size = 2
+        vllm_config = MagicMock()
         speculative_config = MagicMock()
+        model_config = MagicMock()
         speculative_config.num_speculative_tokens = 4
         vllm_config.speculative_config = speculative_config
+        model_config.dtype = torch.float16
+        vllm_config.model_config = model_config
+        get_current_vllm_config.return_value = vllm_config
 
         num_heads = 256
         head_size = 1024
@@ -622,4 +628,4 @@ class TestAscendMLAImpl(TestBase):
 
         self.assertEqual(result.shape[0], B)
         self.assertEqual(result.shape[1], N)
-        self.assertEqual(result.shape[2], HD)
+        self.assertEqual(result.shape[2], HD)