cpus: Restrict cpu_has_work() to system emulation This method is not used on user emulation, because there is always work to do there. Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-Id: <20250125170125.32855-2-philmd@linaro.org>