[llvm] [LV] Explicitly disallow interleaved access requiring gap mask for scalable VFs. nfc (PR #154122)

[Luke Lau via llvm-commits]

https://github.com/lukel97 approved this pull request.

LGTM, thanks for making this more explicit. I also checked AArch64 and their TTI doesn't allow scalable VFs with `UseMaskForGaps` either.

https://github.com/llvm/llvm-project/pull/154122