[RISCV] Fold (sub constant, (setcc x, y, eq/neq)) -> (add constant - 1, (setcc x, y, neq/eq))

(setcc x, y, eq/neq) are seqz, snez that set rd = 0/1.

addi is used to process immediate, which can save instructions for load immediate.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D131471