Need a FAQ or doc to tell users how to not quant some layers in quant-aware training.
Created by: qingqing01
related to https://github.com/PaddlePaddle/PaddleSlim/issues/364#issuecomment-651183736
FAQ: https://paddleslim.readthedocs.io/zh_CN/latest/FAQ/quantization_FAQ.html#id2