LoopSimplify: Preserve DependenceAnalysis.

LoopSimplify: Preserve DependenceAnalysis.

This is currently true, but may change when DA grows more aggressive caching.
Without this setting it's impossible to use DA from a LoopPass because DA is a
function pass and cannot be properly scheduled in between LoopPasses. The
LoopManager reacts to this with an infinite loop which made this really annoying
to debug.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166788 91177308-0d34-0410-b5e6-96231b3b80d8