[llvm] [RISCV][GISel] Support G_ROTL/G_ROTR with Zbb. (PR #72825)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

> This would be a good exercise for the new LLVM blessed stacked PR support.

@aemerson Do you mind providing a link where I can read more about this? I didn't see any update on discourse nor do I see it on the [LLVM GitHub Guide](https://llvm.org/docs/GitHub.html).

https://github.com/llvm/llvm-project/pull/72825