[llvm] [RISCV][TTI] Add vp.fneg intrinsic cost with functionalOP (PR #114378)

[Elvis Wang via llvm-commits]

https://github.com/ElvisWang123 approved this pull request.

Overall, LG. But please wait #114184 since the maintainer concern on the test case modification.

https://github.com/llvm/llvm-project/pull/114378