[Bugfix] fix moe_wna16 get_quant_method

[jinzhen-lin]

Fix #12647
The get_quant_method of moe_wna16 always return moe method, GPTQ-based linear method or AWQ-based linear method, even when the target module is attention layer.

vllm/vllm/attention/layer.py

Lines 86 to 92 in baeded2

	quant_method = quant_config.get_quant_method(
	self, prefix=prefix) if quant_config else None
	if quant_method is not None:
	assert isinstance(quant_method, BaseKVCacheMethod)
	# TODO (mgoin): kv cache dtype should be specified in the FP8
	# checkpoint config and become the "auto" behavior

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