merge fully_connected_rowwise_dnnlowp_op into fully_connected_dnnlowp_op (#17105)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17105
To make FC with rowwise quantization faster, reduce code duplication, and make code consistent with Convolution
Reviewed By: csummersea
Differential Revision: D14080461
fbshipit-source-id: 2b0e67b86e7e3029c90751a8824bf80ae1223680
