[sanitizer] Revert rL324263

Summary:
The 32-bit division  breaks SizeClassAllocator64PopulateFreeListOOM which uses
Primary that has a maximum size > 32-bit.

Reviewers: alekseyshl

Subscribers: kubamracek, delcypher, #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D42928

llvm-svn: 324268