[msan] Avoid extra origin address realignment.

Do not realign origin address if the corresponding application
address is at least 4-byte-aligned.

Saves 2.5% code size in track-origins mode.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223464 91177308-0d34-0410-b5e6-96231b3b80d8