[quant] Make offsets an optional argument (#43090)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43090
To match the floating point module
Test Plan: Imported from OSS
Reviewed By: vkuzo
Differential Revision: D23167518
fbshipit-source-id: 29db596e10731be4cfed7efd18f33a0b3dbd0ca7
