Revert "[SCEV] Cache results of computeExitLimit"

This reverts commit r309080.  The patch needs to clear out the
ScalarEvolution::ExitLimits cache in forgetMemoizedResults.

I've replied on the commit thread for the patch with more details.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309357 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed