[llvm] [RISCV][CostModel] Add getRISCVInstructionCost() to TTI for Cost… (PR #73651)

[Shih-Po Hung via llvm-commits]

arcbbb wrote:

> This breaks a few bots with https://lab.llvm.org/buildbot/#/builders/168/builds/17710
> 
> Should we revert it?

@vitalybuka Thanks! I am still trying to reproduce this in my local.

https://github.com/llvm/llvm-project/pull/73651