Bluetooth: Remove unnecessary smp_mb__{before,after}_atomic

The barriers are unneeded; wait_woken() and woken_wake_function()
already provide us with the required synchronization: remove them
and document that we're relying on the (implicit) synchronization
provided by wait_woken() and woken_wake_function().

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Reviewed-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/bnep/core.c

@@ -489,9 +489,6 @@ static int bnep_session(void *arg)
 
 	add_wait_queue(sk_sleep(sk), &wait);
 	while (1) {
-		/* Ensure session->terminate is updated */
-		smp_mb__before_atomic();
-
 		if (atomic_read(&s->terminate))
 			break;
 		/* RX */
@@ -512,6 +509,10 @@ static int bnep_session(void *arg)
 				break;
 		netif_wake_queue(dev);
 
+		/*
+		 * wait_woken() performs the necessary memory barriers
+		 * for us; see the header comment for this primitive.
+		 */
 		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 	}
 	remove_wait_queue(sk_sleep(sk), &wait);