handle the case of -0.0 on tanh quantization (#44406)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44406
this fix makes fakelowp identical to hw
- mask out the floating point number with 0x7fff so we are always dealing
with positive numbers
- dsp implementation is correct, ice-ref suffers from this same problem
Test Plan: - tested with test_fusions.py, can't enable the test until the fix in ice-ref appears
Reviewed By: venkatacrc
Differential Revision: D23603878
fbshipit-source-id: a72d93a4bc811f98d1b5e82ddb204be028addfeb
