[RISCV] Don't fold (sub C, (setcc x, y, eq/neq)) -> (add C-1, (setcc x, y,...

[RISCV] Don't fold (sub C, (setcc x, y, eq/neq)) -> (add C-1, (setcc x, y, neq/eq)) if C-1 isn't simm12.

We still need to materialize the constant in a register and we
may not be removing all uses of the original constant so it may
increase code size.