[llvm] [VPlan] Directly retrieve metadata in getMemoryLocation (NFC) (PR #169028)

[Florian Hahn via llvm-commits]

https://github.com/fhahn approved this pull request.

LGTM, thanks.

For the titel, maybe clarify that this use dyn_cast to VPIRMetadata

https://github.com/llvm/llvm-project/pull/169028