iio: event: Add missing fields in kernel docs

Fix kernel docs warnings by adding the missing fields,
each with its associated description.
Signed-off-by: NCristina Opriceana <cristina.opriceana@gmail.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

drivers/iio/industrialio-event.c

@@ -32,6 +32,7 @@
  * @dev_attr_list:	list of event interface sysfs attribute
  * @flags:		file operations related flags including busy flag.
  * @group:		event interface sysfs attribute group
+ * @read_lock:		lock to protect kfifo read operations
  */
 struct iio_event_interface {
 	wait_queue_head_t	wait;
@@ -75,6 +76,11 @@ EXPORT_SYMBOL(iio_push_event);
 
 /**
  * iio_event_poll() - poll the event queue to find out if it has data
+ * @filep:	File structure pointer to identify the device
+ * @wait:	Poll table pointer to add the wait queue on
+ *
+ * Return: (POLLIN | POLLRDNORM) if data is available for reading
+ *	   or a negative error code on failure
  */
 static unsigned int iio_event_poll(struct file *filep,
 			     struct poll_table_struct *wait)