[llvm] [RISCV][VLOPT] Fix passthru check in getOperandInfo (PR #112244)

[Luke Lau via llvm-commits]

lukel97 wrote:

> > Do we need to fix in isVectorOpUsedAsScalarOp too?
> 
> I think isVectorOpUsedAsScalarOp is actually correct currently, but because HasPassthru is always true.

Actually I think I was wrong, I think the scalar ops should be 1 (vd) and 3 (vs1). But this can be fixed in a separate PR

https://github.com/llvm/llvm-project/pull/112244