[S390] use set_current_state in sigsuspend

Use set_current_state instead of a direct assignment to set the
task state of the current process.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/signal.c

@@ -64,7 +64,7 @@ SYSCALL_DEFINE3(sigsuspend, int, history0, int, history1, old_sigset_t, mask)
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	current->state = TASK_INTERRUPTIBLE;
+	set_current_state(TASK_INTERRUPTIBLE);
 	schedule();
 	set_thread_flag(TIF_RESTORE_SIGMASK);