change return type for q_scale and q_zero_point (#21709)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21709
Change the return type from Scalar to double/int64_t so we don't need to do conversion when we call other quantize related aten functions
Differential Revision: D15793003
fbshipit-source-id: 510936c69fa17a4d67340a31ebb03415647feb04
