Turn off scalar_check for _th_addmv and _th_eig as they can never pass. (#29945)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29945
Both functions require at least 1 2-dimensional tensor, so can never return an inferred scalar.
Test Plan: Imported from OSS
Differential Revision: D18548056
Pulled By: gchanan
fbshipit-source-id: f99a41d490b9a5ab5717534c92e4f2e848c743e8
