[XNNPACK] Expose available() to xnnpack namespace (#73617)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73617
Linter doesn't like a call to xnnpack::internal::available() from outside the namespace
Reviewed By: kimishpatel
Differential Revision: D33641389
fbshipit-source-id: ac7a63a580a5427d1995cdb7da4398ec1bb23c11
(cherry picked from commit 11756d51fd71d326a0cf134803e51b6b235b0c20)
