[esan|wset] Fix incorrect memory size assert

Summary:
Fixes an incorrect assert that fails on 128-bit-sized loads or stores.
Augments the wset tests to include this case.

Reviewers: aizatsky

Subscribers: vitalybuka, zhaoqin, kcc, eugenis, llvm-commits

Differential Revision: http://reviews.llvm.org/D22062

llvm-svn: 274666