Init attention backend for Intel XPU (#10656)

Co-authored-by: guangyey <guangye.yu@intel.com>
Co-authored-by: DiweiSun <105627594+DiweiSun@users.noreply.github.com>

python/sglang/srt/layers/rotary_embedding.py

@@ -115,7 +115,7 @@ class RotaryEmbedding(CustomOp):
         if dtype == torch.float32 or (
             (not (_is_cuda or _is_npu) or self.head_size not in [64, 128, 256, 512])
             and not (_is_cpu and _is_cpu_amx_available)
-            and not _is_xpu
+            and not (_is_xpu)
         ):
             from vllm._custom_ops import rotary_embedding
 
@@ -302,6 +302,7 @@ class RotaryEmbedding(CustomOp):
         offsets: Optional[torch.Tensor] = None,
     ) -> Tuple[torch.Tensor, torch.Tensor]:
         # TODO: make a wrapper, and XPU will implement this kernel later.
+        self.cos_sin_cache = self.cos_sin_cache.to(query.device)
         return self.forward_native(positions, query, key, offsets)