[llvm] [RISCV] Reverse default assumption about performance of vlseN.v vd, (rs1), x0 (PR #98205)

[Luke Lau via llvm-commits]

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

I can also reproduce the spacemit-x60 not having optimised x0-stride vlses.

https://github.com/llvm/llvm-project/pull/98205