[csrc][bugfix] Add compile-time Ascend950/910_95 compatibility for custom ops between CANN8.5 and 9.0 (#6936)

### What this PR does / why we need it?
Remove hardcoded ASCEND910_95 usage in csrc custom-op host/tiling code
and
select the SoC target at CMake configure time.

- Probe CANN headers with check_cxx_source_compiles:
prefer platform_ascendc::SocVersion::ASCEND950, fallback to
ASCEND910_95.
- Export the selected enum/config string via shared compile definitions
(VLLM_ASCEND_950_SOC_ENUM / VLLM_ASCEND_950_SOC_CONFIG).
- Apply the shared macros to affected paths (moe_gating_top_k,
add_rms_norm_bias) to avoid per-file hardcoding.
- Keep behavior unchanged; this is an internal build-compatibility fix
for CANN 8.5 and 9.x.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?

- vLLM version: v0.16.0
- vLLM main:
15d76f74e2

---------

Signed-off-by: linfeng-yuan <1102311262@qq.com>

csrc/moe_init_routing_custom/op_host/moe_init_routing_custom_tiling.cpp

@@ -1263,5 +1263,5 @@ void MoeInitRountingCustomTilingBase::Tiling4GatherOutCompute()
         lastCorePerLoopIndicesElements, lastCoreLastLoopIndicesElements);
 }
 
-REGISTER_TILING_TEMPLATE("MoeInitRoutingCustom", MoeInitRountingCustomTilingBase, 10000); // If not 910_95, fallback to this.
-} // namespace optiling
+REGISTER_TILING_TEMPLATE("MoeInitRoutingCustom", MoeInitRountingCustomTilingBase, 10000); // Fallback template for non-Ascend950 SoC.
+} // namespace optiling