Upgrade mkldnn to version 0.18.1 (#18463)
Summary:
Upgrade mkldnn to version 0.18.1
Fix the MKLDNN build issue if linking with MKL 2019.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18463
Differential Revision: D14620228
Pulled By: ezyang
fbshipit-source-id: 136074ad0e4631e1dde4ca1b0af4ee6a41e50913
