af_iucv: fix race in __iucv_sock_wait()

Moving prepare_to_wait before the condition to avoid a race between
schedule_timeout and wake up.
The race can appear during iucv_sock_connect() and iucv_callback_connack().
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/iucv/af_iucv.c

@@ -59,8 +59,8 @@ do {									\
 	DEFINE_WAIT(__wait);						\
 	long __timeo = timeo;						\
 	ret = 0;							\
-	while (!(condition)) {						\
 	prepare_to_wait(sk->sk_sleep, &__wait, TASK_INTERRUPTIBLE);	\
+	while (!(condition)) {						\
 		if (!__timeo) {						\
 			ret = -EAGAIN;					\
 			break;						\