[llvm] [VPlan] Use DL index type consistently for GEPs (PR #169396)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> Could you link the unroll PR and add expand to the motivation, clarifying how this helps with it?

Added link and line "The patch also helps by doing a mass test update up-front.", thanks.

https://github.com/llvm/llvm-project/pull/169396