[asan] Fix size of shadow incorrectly calculated in r279178

Summary: r279178 generates 8 times more stores than necessary.

Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23708

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279222 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed