[Bugfix] Support MLA for CompressedTensorsWNA16

[mgoin]

Without this change, models that use CompressedTensorsWNA16 will fail with MLA enabled due to their usage of weight_packed

Reference:

vllm/vllm/model_executor/layers/quantization/compressed_tensors/schemes/compressed_tensors_wNa16.py

Line 137 in db986c1

layer.register_parameter("weight_packed", weight)

Error:

[rank0]:   File "/home/mgoin/code/vllm/vllm/attention/backends/mla/common.py", line 1155, in process_weights_after_loading
[rank0]:     weight_dtype = get_layer_weight(self.kv_b_proj).dtype
[rank0]:                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[rank0]:   File "/home/mgoin/code/vllm/vllm/attention/backends/mla/common.py", line 1138, in get_layer_weight
[rank0]:     raise AttributeError(
[rank0]: AttributeError: Layer 'ColumnParallelLinear(in_features=512, output_features=4096, bias=False, tp_size=1, gather_output=False)' has neither weight nor qweight

[github-actions]

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