[llvm] [RISCV] Refine cost on Min/Max reduction (PR #79402)

[Han-Chung Wang via llvm-commits]

hanhanW wrote:

> Reverted, @arcbbb please post a new version with support for the two missing cases. You can reuse this PR if desired.

Thanks!

https://github.com/llvm/llvm-project/pull/79402