Revert "[IVDescriptors] Add pointer InductionDescriptors with non-constant strides"

Multiple errors have being reported on
https://reviews.llvm.org/rG498aa534f472d28db893aa9a8627d0b46e17f312

Reverting until the correctness issues can be resolved.

We are also seeing a lot of performance differences from the patch.  Some are
looking good, but some are looking pretty bad.