Use is_flashinfer_available to replace is_hip for flashinfer check (#1596)

Co-authored-by: Zhang Liangang <liangang.zhang@intel.com>

python/sglang/srt/utils.py

@@ -50,11 +50,19 @@ show_time_cost = False
 time_infos = {}
 
 
-# torch flag AMD GPU
 def is_hip() -> bool:
+    """Return whether it is HIP on the AMD ROCm platform."""
     return torch.version.hip is not None
 
 
+def is_flashinfer_available():
+    """
+    Check whether flashinfer is available.
+    As of Oct. 6, 2024, it is only available on NVIDIA GPUs.
+    """
+    return torch.cuda.is_available() and not is_hip()
+
+
 def is_ipv6(address):
     try:
         ipaddress.IPv6Address(address)