[llvm] [RISCV][IA] Always generate masked versions of segment LD/ST [nfc-ish] (PR #148905)

[Luke Lau via llvm-commits]

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

LGTM. I swear I thought we already did this because I remember pointing this out in a PR review, but then I realised it was for the VP lowering path.

https://github.com/llvm/llvm-project/pull/148905