Revert r330376 "[sanitizer] Generalize atomic_uint8_t, atomic_uint16_t, ... into a template. NFC."

This broke the Windows build, see e.g. http://lab.llvm.org:8011/builders/clang-x64-ninja-win7/builds/10130

> Differential Revision: https://reviews.llvm.org/D44246

llvm-svn: 330395