[Misc] Clean Up EngineArgs.create_engine_config (#13734)

Signed-off-by: rshaw@neuralmagic.com <rshaw@neuralmagic.com>

vllm/config.py

@@ -1124,6 +1124,10 @@ class CacheConfig:
         return {key: str(value) for key, value in self.__dict__.items()}
 
     def _verify_args(self) -> None:
+        if self.cpu_offload_gb < 0:
+            raise ValueError("CPU offload space must be non-negative"
+                             f", but got {self.cpu_offload_gb}")
+
         if self.gpu_memory_utilization > 1.0:
             raise ValueError(
                 "GPU memory utilization must be less than 1.0. Got "