[llvm] [RISCV][GISel] Lower G_ABDS and G_ABDU (PR #155888)

[Shaoce SUN via llvm-commits]

sunshaoce wrote:

> Isn't the code in LowerOperation only used for vectors?

>From what I saw, `lowerAbsDiffToMinMax` works for both scalars and vectors. Should we keep it generic?

https://github.com/llvm/llvm-project/pull/155888