groupsize=64 is not supported

[jameswu2014]

Hello, Marlin is a great job! However, in my use case, I found that it still has some limitations. Specifically, when the group size of GPTQ is set to 64, the model performs very well; when set to 128, the performance will decrease. However, Marlin currently does not support setting the group size to 64. Therefore, I would like to ask, how can I modify the source code to make Marlin support this setting?