[llvm] [RISCV][VLOPT] Add fp-reductions to getOperandInfo (PR #122151)

[Philip Reames via llvm-commits]

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

LGTM - though you'll need to rebase over the recently landed getOperandLog2EEW change.  As long as you consider the rebase straight forward, no need for further review.  

https://github.com/llvm/llvm-project/pull/122151