linux-user: Handle NULL sched_param argument to sched_* The sched_getparam, sched_setparam and sched_setscheduler system calls take a pointer argument to a sched_param structure. When this pointer is null, errno should be set to EINVAL. Signed-off-by: Tom Musta <tommusta@gmail.com> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>