[platforms] absorb worker cls difference into platforms folder (#10555)

Signed-off-by: youkaichao <youkaichao@gmail.com>
Co-authored-by: Nick Hill <nhill@redhat.com>

vllm/platforms/xpu.py

@@ -57,6 +57,10 @@ class XPUPlatform(Platform):
                 "mode.")
             model_config.enforce_eager = True
 
+        if vllm_config.speculative_config is not None:
+            raise NotImplementedError(
+                "XPU does not support speculative decoding")
+
         # check and update parallel config
         parallel_config = vllm_config.parallel_config
         if (parallel_config.distributed_executor_backend is not None
@@ -66,3 +70,5 @@ class XPUPlatform(Platform):
                 " executor backend.",
                 parallel_config.distributed_executor_backend)
             parallel_config.distributed_executor_backend = "ray"
+        if parallel_config.worker_cls == "auto":
+            parallel_config.worker_cls = "vllm.worker.xpu_worker.XPUWorker"