[HWASan] Add "N" suffix to generic __hwasan_load/store.

Summary:
"N" suffix is added by the instrumentation and interface functions
are expected to be exported from the library as __hwasan_loadN* and
__hwasan_storeN*.

Reviewers: eugenis

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

Differential Revision: https://reviews.llvm.org/D45739

llvm-svn: 330297