[llvm] [RISCV] Add missing hasPostISelHook = 1 to vector pseudos that might read FRM. (PR #114186)

[Pengcheng Wang via llvm-commits]

https://github.com/wangpc-pp commented:

I don't know if I understand correctly, we don't add `frm` operand for some cases before?

https://github.com/llvm/llvm-project/pull/114186