[llvm] [RISCV] Preserve tail agnostic policy in some vector peepholes (PR #105788)

[Philip Reames via llvm-commits]

preames wrote:

Can you say a bit about why this helps?  It seems slightly odd to me that we need to preserve the policy here.  How does doing so fit into your next step?

https://github.com/llvm/llvm-project/pull/105788