[llvm] [RISCV] Remove setJumpIsExpensive(). (PR #74647)

[Alex Bradbury via llvm-commits]

asb wrote:

> How about adding it to `RISCVSubtarget` and changing it to something like:
> 
> ```c
> setJumpIsExpensive(Subtarget.isJumpExpensive())
> ```
> 
> So that processors can tune it.

Do you have a target where you actively want to support that configuration? I agree this is something that could be made configurable, but we're probably best off focusing our efforts around a smaller set of configuration options unless we know there's a case where we really need to diverge.

https://github.com/llvm/llvm-project/pull/74647