[llvm] [RISCV] Only calculate ordered reduction with FloatingPoint type. NFC (PR #114180)

[Elvis Wang via llvm-commits]

ElvisWang123 wrote:

I am worried about  transformations using `getArithmeticReductionCost()` directly  to query the instruction cost and not dropping the FMF flags with integer type.
After investigation, all query will not return wrong instruction cost currently. 

I am fine to close this PR.

https://github.com/llvm/llvm-project/pull/114180