[Feature] Add quant description file for new quant model generated by modelslim (#719)

### What this PR does / why we need it?
After discussed with MindStudio about the quantization model format, we
decide to support another quant format which may used in new modelslim
tool, in which case, `quantization_config` may be removed from the
`config.json` file and `quant_model_description.json` will be used for
quantization configuration.
### Does this PR introduce _any_ user-facing change?
Yes, using the latest quantization format

### How was this patch tested?
Test locally

Signed-off-by: ganyi <pleaplusone.gy@gmail.com>

vllm_ascend/quantization/quant_config.py

@@ -67,7 +67,7 @@ class AscendQuantConfig(QuantizationConfig):
 
     @classmethod
     def get_config_filenames(cls) -> List[str]:
-        return []
+        return ["quant_model_description.json"]
 
     @classmethod
     def from_config(cls, config: Dict[str, Any]) -> "AscendQuantConfig":