[Attention] Use `has_flashinfer` helper (#33177)

Signed-off-by: Matthew Bonanni <mbonanni@redhat.com>

vllm/model_executor/layers/attention/mla_attention.py

@@ -229,7 +229,7 @@ from vllm.model_executor.layers.quantization.utils.quant_utils import (
     get_and_maybe_dequant_weights,
 )
 from vllm.platforms import current_platform
-from vllm.utils.flashinfer import has_nvidia_artifactory
+from vllm.utils.flashinfer import has_flashinfer, has_nvidia_artifactory
 from vllm.utils.math_utils import cdiv, round_down
 from vllm.utils.torch_utils import (
     direct_register_custom_op,
@@ -599,13 +599,6 @@ except ImportError:
     is_vllm_fa = False
 
 
-@functools.cache
-def flashinfer_available() -> bool:
-    import importlib.util
-
-    return importlib.util.find_spec("flashinfer") is not None
-
-
 def dynamic_per_batched_tensor_quant(
     x: torch.Tensor, dtype: torch.dtype = torch.float8_e4m3fn
 ):
@@ -824,7 +817,7 @@ def use_flashinfer_prefill() -> bool:
     vllm_config = get_current_vllm_config()
     if not (
         not vllm_config.attention_config.disable_flashinfer_prefill
-        and flashinfer_available()
+        and has_flashinfer()
         and not vllm_config.attention_config.use_cudnn_prefill
         and current_platform.is_device_capability_family(100)
     ):
@@ -838,7 +831,7 @@ def use_cudnn_prefill() -> bool:
 
     vllm_config = get_current_vllm_config()
     return (
-        flashinfer_available()
+        has_flashinfer()
         and vllm_config.attention_config.use_cudnn_prefill
         and current_platform.is_device_capability_family(100)
         and has_nvidia_artifactory()
@@ -851,7 +844,7 @@ def use_trtllm_ragged_deepseek_prefill() -> bool:
 
     vllm_config = get_current_vllm_config()
     if not (
-        flashinfer_available
+        has_flashinfer()
         and vllm_config.attention_config.use_trtllm_ragged_deepseek_prefill
         and current_platform.is_device_capability_family(100)
     ):