staging: iio: Fix incorrect existence check for a shared event pointer.

A second smatch detected error. First part fixes in a typo
in the comment directly above that I noticed whilst trying
to remember what this code actually does. Second part is
the actual fix.  I'm fairly amazed this one never caused
trouble in testing as it is in one of the most common paths.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/industrialio-core.c

@@ -292,16 +292,16 @@ ssize_t iio_event_chrdev_read(struct file *filep,
 	mutex_unlock(&ev_int->event_list_lock);
 	/*
 	 * Possible concurency issue if an update of this event is on its way
-	 * through. May lead to new even being removed whilst the reported event
-	 * was the unescalated event. In typical use case this is not a problem
-	 * as userspace will say read half the buffer due to a 50% full event
-	 * which would make the correct 100% full incorrect anyway.
+	 * through. May lead to new event being removed whilst the reported
+	 * event was the unescalated event. In typical use case this is not a
+	 * problem as userspace will say read half the buffer due to a 50%
+	 * full event which would make the correct 100% full incorrect anyway.
 	 */
-	spin_lock(&el->shared_pointer->lock);
-	if (el->shared_pointer)
+	if (el->shared_pointer) {
+		spin_lock(&el->shared_pointer->lock);
 		(el->shared_pointer->ev_p) = NULL;
-	spin_unlock(&el->shared_pointer->lock);
-
+		spin_unlock(&el->shared_pointer->lock);
+	}
 	kfree(el);
 
 	return len;