[llvm] [RISCV][NFC] Remove unused getSelectionDAGInfo (PR #98172)

[Craig Topper via llvm-commits]

topperc wrote:

I'm not sure what you mean by "never set". The RISCVSubtarget creates an instance of `SelectionDAGTargetInfo`. This access returns a pointer to it. Is there nothing in the generic `SelectionDAGTargetInfo` that we need? Multiple targets do the same thing.

https://github.com/llvm/llvm-project/pull/98172