[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>
diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
index 1675c48..6289945 100644
--- a/arch/s390/kernel/signal.c
+++ b/arch/s390/kernel/signal.c
@@ -64,7 +64,7 @@
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	current->state = TASK_INTERRUPTIBLE;
+	set_current_state(TASK_INTERRUPTIBLE);
 	schedule();
 	set_thread_flag(TIF_RESTORE_SIGMASK);