Get QScheme from observer module (#31293)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31293
Previously we check the number of elements in scale to determine if we are using per channel quantization,
but we should get qscheme information from observer module directly and we'll expose this information
to caller as well
Test Plan:
.
Imported from OSS
Differential Revision: D19146669
fbshipit-source-id: ea430eeae0ef8f441be39aa6dcc1bb530b065554
