[LoopAccesses] Stash the report from the analysis rather than emitting it

[LoopAccesses] Stash the report from the analysis rather than emitting it

The transformation passes will query this and then emit them as part of
their own report.  The currently only user LV is modified to do just
that.

This is part of the patchset that converts LoopAccessAnalysis into an
actual analysis pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229623 91177308-0d34-0410-b5e6-96231b3b80d8