[3/N][Refactor][Quantization]remove packed_modules_mapping from models (#3021)

### What this PR does / why we need it?

Some custom models in vllm-ascend define packed_modules_mapping, which
prevent keeping same model class with vllm community. So move these
custom packed_modules_mapping to quant utils.py. After this pr, some
custom models can be removed.

### Does this PR introduce _any_ user-facing change?

tested by CI

### How was this patch tested?

tested by CI

- vLLM version: v0.10.2
- vLLM main:
5089fd749c

Signed-off-by: 22dimensions <waitingwind@foxmail.com>

vllm_ascend/models/deepseek_v2.py

@@ -320,12 +320,6 @@ class CustomDeepseekV2DecoderLayer(DeepseekV2DecoderLayer):
 
 
 class CustomDeepseekV2ForCausalLM(DeepseekV2ForCausalLM):
-    # add `packed_modules_mapping` in `DeepseekV2ForCausalLM` to support weight merging
-    packed_modules_mapping = {
-        "gate_up_proj": ["gate_proj", "up_proj"],
-        "experts":
-        ["experts.0.gate_proj", "experts.0.up_proj", "experts.0.down_proj"]
-    }
 
     def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
         nn.Module.__init__(self)