[llvm] [RISCV] Lower unmasked zero-stride vp.stride to a splat of one scalar load. (PR #97394)

[Yeting Kuo via llvm-commits]

yetingk wrote:

Close the ticket since it's too hard to know evl operand is nonzero in compiler time. 

https://github.com/llvm/llvm-project/pull/97394