cleanup ascend config (#5296)

1. refresh additional config doc
2. move kv config logic to platform.
3. improve `dump_config` init logic and rename it to `dump_config_path`
this change is user impacted. dump_config is changed from dict to
string.
4. correct `enable_async_exponential` type
5. remove useless `chunked_prefill_for_mla`

- vLLM version: release/v0.13.0
- vLLM main:
ad32e3e19c

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

vllm_ascend/sample/sampler.py

@@ -83,7 +83,7 @@ class AscendTopKTopPSampler(TopKTopPSampler):
             logits_to_return = logits.log_softmax(dim=-1, dtype=torch.float32)
 
         probs = logits.softmax(dim=-1, dtype=torch.float32)
-        if get_ascend_config().enable_async_exponential == 1:
+        if get_ascend_config().enable_async_exponential:
             # Add synchronize to prevent synchronize error.
             self.async_event.synchronize()
             return probs.div_(self.q).argmax(dim=-1).view(-1), logits_to_return