Changing the sign before rounding affects the correctness of
the asymmetric rouding modes: float_round_up and float_round_down.
Reported-by: WANG Rui <wangrui@loongson.cn>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
