target/riscv: Remove gen_arith_div*

target/riscv: Remove gen_arith_div*

Use ctx->w and the enhanced gen_arith function.

Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210823195529.560295-8-richard.henderson@linaro.org
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>