[llvm] [GISel][RISCV]Implement indirect parameter passing for large scalars (PR #95429)

[Craig Topper via llvm-commits]

topperc wrote:

> I wrote this assuming that lowering of large integer types is intentionally left to the backend, which doesn't appear so.

Looks like we intentionally defer the handling for scalars to the backend. Except for _BitInt

https://github.com/llvm/llvm-project/pull/95429