Make the default qconfig_dict (#24232)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/24232
As suggested in https://github.com/pytorch/pytorch/pull/23128#discussion_r306650311, we will make the keys of default_qconfig_dict as `torch.nn.Linear`. That is, we will do the dynamic quantization on the `torch.nn.Linear` by default, if the user just specify `torch.quantize_dynamic(model)`.
ghstack-source-id: 88287089
Differential Revision: D16781191
fbshipit-source-id: 991a5e151a9ea32b879d6897cd9862855d747135
