[Platform] move current_memory_usage() into platform (#11369)

Signed-off-by: Shanshan Shen <467638484@qq.com>

vllm/platforms/xpu.py

@@ -94,3 +94,10 @@ class XPUPlatform(Platform):
     def is_pin_memory_available(cls):
         logger.warning("Pin memory is not supported on XPU.")
         return False
+
+    @classmethod
+    def get_current_memory_usage(cls,
+                                 device: Optional[torch.types.Device] = None
+                                 ) -> float:
+        torch.xpu.reset_peak_memory_stats(device)
+        return torch.xpu.max_memory_allocated(device)