[clang] [llvm] [RISC-V][RVY] Rank 'y' after 'i' and 'e' in canonical extension order (PR #227865)

[Sam Elliott via cfe-commits]

https://github.com/lenary approved this pull request.

This change LGTM, but also agreed that we want to do more of the Y stuff at the same time.

https://github.com/llvm/llvm-project/pull/227865