NNAPI: Add qint16 support via int16 (#70621)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70621
Pytorch doesn't have support for qint16 yet. Add an option to handle qint16 via int16 & qint32 data types.
* For qint16 tensors in NNAPI, the user sends a qint32 tensor. We convert the qint32 to int16 for the converter and set the zero point and scale for nnapi
* inputs to the model have to have fixed scale and zero point and are only supported for testing
* Added a flag use_int16_for_qint16 which will be used maintain backwards compatibility in the converter when true qint16 is supported in PyTorch
ghstack-source-id: 146507483
Test Plan: pytest test/test_nnapi.py
Reviewed By: dreiss
Differential Revision: D33285124
fbshipit-source-id: b6376fa1bb18a0b9f6a18c545f600222b650cb66
