LoopRotate: Reorder some method implementations. NFC

LoopRotate: Reorder some method implementations. NFC

This just moves some callers after their callees. My next patch will
convert some of these methods to stand alone functions, and that diff
is more obviously NFC if I move these first. That change, in turn,
will make it much easier to port this pass to the new pass manager
once the loop pass manager is in place.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255573 91177308-0d34-0410-b5e6-96231b3b80d8