Fix the other comment to use modern doxygen style and be a bit more
direct. Notably, comment on the fact that the loaded type is significant
in that it determines how wide of an access must be safe.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220150 91177308-0d34-0410-b5e6-96231b3b80d8