[llvm] [RISCV] RISCV vector calling convention (2/2) (PR #79096)

[Brandon Wu via llvm-commits]

4vtomat wrote:

> @4vtomat the [LLVM dev policy](https://llvm.org/docs/DeveloperPolicy.html#patch-reversion-policy) mandates reverts instead of fixes forward to keep the tree healthy.
> 
> Please revert first to unblock all other teams that are hindered by this issue, investigate the issue offline, and then reapply the fixed patch.

Got it, thanks~

https://github.com/llvm/llvm-project/pull/79096