[Refact.]: Refactor some leftover implementations of 300I DUO in the main branch. (#6425)

### What this PR does / why we need it?
- Replace the RoPE operator implementation.
- Refactor some leftover implementations of 300I DUO in the main branch.

### Does this PR introduce _any_ user-facing change?
NA
### How was this patch tested?

- vLLM version: v0.14.1
- vLLM main:
dc917cceb8

---------

Signed-off-by: Tflowers-0129 <2906339855@qq.com>

vllm_ascend/_310p/ops/layernorm.py

@@ -11,17 +11,16 @@ class AscendRMSNorm310(AscendRMSNorm):
         residual: torch.Tensor | None = None,
     ) -> torch.Tensor | tuple[torch.Tensor, torch.Tensor]:
         if residual is not None:
-            orig_dtype = residual.dtype
             if x is None or x.numel() == 0 or x.shape[-1] == 0:
-                x = residual.to(dtype=residual.dtype)
+                x = residual
             else:
-                x = x + residual.to(x.dtype)
+                x = x + residual
 
-            residual = x.to(orig_dtype)
+            residual = x
             x, _ = torch_npu.npu_rms_norm(x, self.weight, self.variance_epsilon)
             return x, residual
 
-        x, residual = torch_npu.npu_rms_norm(x, self.weight, self.variance_epsilon)
+        x, _ = torch_npu.npu_rms_norm(x, self.weight, self.variance_epsilon)
         if self.bias is not None:
             x.add_(self.bias)
         return x