Revert "[SCEV] Maintain and use a loop->loop invalidation dependency"

This reverts commit r315713.  It causes PR34968.

I think I know what the problem is, but I don't think I'll have time to fix it
this week.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315962 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed