[clang] [llvm] [RISCV] Add support for vector registers with -fzero-call-used-regs (PR #206206)

[Craig Topper via cfe-commits]

topperc wrote:

> I rebased the branch on top of main to solve the merge conflicts on `clang/docs/ReleaseNotes.md`.

Please merge main instead of rebasing and force pushing.

https://github.com/llvm/llvm-project/pull/206206