[llvm] [RISCV] Disable performCombineVMergeAndVOps for PseduoVIOTA_M. (PR #71483)

[Yeting Kuo via llvm-commits]

yetingk wrote:

Address @lukel97's idea to add a bit into `RISCVMaskedPseudoInfo` to represent the operation value is related to mask.

https://github.com/llvm/llvm-project/pull/71483