[Hardware][XPU] Align memory usage with cuda on xpu (#37029)

Signed-off-by: Kunshang Ji <jikunshang95@gmail.com>
Signed-off-by: Kunshang Ji <kunshang.ji@intel.com>

vllm/platforms/xpu.py

@@ -236,6 +236,7 @@ class XPUPlatform(Platform):
     def get_current_memory_usage(
         cls, device: torch.types.Device | None = None
     ) -> float:
+        torch.xpu.empty_cache()
         torch.xpu.reset_peak_memory_stats(device)
         return torch.xpu.max_memory_allocated(device)