[Deepseek V3.2] Enable flashmla_auto with MTP (#12294)

Signed-off-by: Hao Lu <14827759+hlu1@users.noreply.github.com>

python/sglang/srt/layers/attention/nsa_backend.py

@@ -1222,11 +1222,9 @@ class NativeSparseAttnBackend(AttentionBackend):
         if self.enable_auto_select_prefill_impl:
             if self.nsa_kv_cache_store_fp8:
                 if (
-                    # TODO(hlu1): enable MTP
                     is_blackwell()
                     and forward_batch is not None
-                    and forward_batch.forward_mode.is_extend()
-                    and forward_batch.spec_algorithm.is_none()
+                    and forward_batch.forward_mode == ForwardMode.EXTEND
                 ):
                     total_kv_tokens = forward_batch.seq_lens_sum
                     total_q_tokens = forward_batch.extend_num_tokens