add OpInfo entry for signbit (#52198)
Summary:
Reference: https://github.com/pytorch/pytorch/issues/42515
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52198
Reviewed By: H-Huang
Differential Revision: D26727598
Pulled By: mruberry
fbshipit-source-id: 282350febbd0b1af73320f0e912bf553d386d4b0
