optimize device memory

[Godlovecui]

I found that the device memory usage keeps increasing when execute basic_quant_mix.py, it will raise OOM when model has large parameters, so, how to optimize it. Thank you~
@Qcompiler

[Qcompiler]

OK Since it is NOT required to store the whole model in GPU while quantizing, we will try to fix this problem.
Thanks a lot for your reminder.