iio: event: Remove negative error code from iio_event_poll

Negative return values are not supported by iio_event_poll since
its return type is unsigned int.

Fixes: f18e7a06 ("iio: Return -ENODEV for file operations if the device has been unregistered")
Signed-off-by: Cristina Opriceana <cristina.opriceana@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/industrialio-event.c

@@ -90,7 +90,7 @@ static unsigned int iio_event_poll(struct file *filep,
 	unsigned int events = 0;
 
 	if (!indio_dev->info)
-		return -ENODEV;
+		return events;
 
 	poll_wait(filep, &ev_int->wait, wait);