mlapo add qdown output (#4707)

### What this PR does / why we need it?
This PR adds mlapo operation support qdown of output.
### Does this PR introduce _any_ user-facing change?
mlapo operation add enable_inner_out of input
### How was this patch tested?
CI passed with new added/existing test.


- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c

---------

Signed-off-by: h1074112368 <h1074112368@gmail.com>
Co-authored-by: wangxiyuan <wangxiyuan1007@gmail.com>

csrc/torch_binding_meta.cpp

@@ -81,7 +81,7 @@ at::Tensor sgmv_expand_meta(at::Tensor &x, at::Tensor &weight, at::Tensor &lora_
     return y_out;
 }
 
-std::tuple<at::Tensor &, at::Tensor &, at::Tensor &, at::Tensor &> mla_preprocess(
+std::tuple<at::Tensor &, at::Tensor &, at::Tensor &, at::Tensor &, at::Tensor &> mla_preprocess(
     const at::Tensor &hiddenState,
     const at::Tensor &wdqkv,
     const at::Tensor &descale0,
@@ -106,12 +106,15 @@ std::tuple<at::Tensor &, at::Tensor &, at::Tensor &, at::Tensor &> mla_preproces
     const c10::optional<at::Tensor> &q_nope_scale,
     c10::optional<c10::string_view> cache_mode,
     c10::optional<c10::string_view> quant_mode,
+    c10::optional<bool> enable_inner_out,
     at::Tensor &q_out0,
     at::Tensor &kv_cache_out0,
     at::Tensor &q_out1,
-    at::Tensor &kv_cache_out1)
+    at::Tensor &kv_cache_out1,
+    at::Tensor &inner_out
+    )
 {
-    return {q_out0, kv_cache_out0, q_out1, kv_cache_out1};
+    return {q_out0, kv_cache_out0, q_out1, kv_cache_out1, inner_out};
 }
 
 std::tuple<at::Tensor, at::Tensor, at::Tensor> grouped_matmul_swiglu_quant(