qemu has already considered about some targets may have no traditional
signals. And openrisc's setup_frame() is dummy, but it can be supported
by setup_rt_frame().
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>