[Misc] Add SPDX-FileCopyrightText (#20428)

Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>

vllm/v1/attention/backends/cpu_attn.py

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 import numpy as np
 import torch
 

vllm/v1/attention/backends/flex_attention.py

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 """Attention layer with FlashAttention."""
 
 from dataclasses import dataclass

vllm/v1/attention/backends/mla/cutlass_mla.py

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
 from typing import Any, Optional
 

vllm/v1/attention/backends/rocm_aiter_fa.py

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 """Attention layer with AiterFlashAttention."""
 from dataclasses import dataclass
 from typing import TYPE_CHECKING, Any, Optional