fix THAllocator.cpp (#19759)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19759
ghimport-source-id: 7ccd6e69dfd36ca9d59da59d5ec55f08e58b79f7
Reviewed By: soumith
Differential Revision: D15087651
Pulled By: ljk53
fbshipit-source-id: 536db274f7e725a0170b6f2c462146c08139f341
