media: dvbdev: fix build warning due to comments

Previous commit that introduces reference counter does not add proper
comments, which will lead to warning when building htmldocs. Fix them.

Reported-by: "Stephen Rothwell" <sfr@canb.auug.org.au>
Fixes: 0fc044b2b5 ("media: dvbdev: adopts refcnt to avoid UAF")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

include/media/dvbdev.h

@@ -130,6 +130,7 @@ struct dvb_adapter {
  * struct dvb_device - represents a DVB device node
  *
  * @list_head:	List head with all DVB devices
+ * @ref:	reference counter
  * @fops:	pointer to struct file_operations
  * @adapter:	pointer to the adapter that holds this device node
  * @type:	type of the device, as defined by &enum dvb_device_type.
@@ -200,7 +201,7 @@ struct dvb_device {
 struct dvb_device *dvb_device_get(struct dvb_device *dvbdev);
 
 /**
- * dvb_device_get - Decrease dvb_device reference
+ * dvb_device_put - Decrease dvb_device reference
  *
  * @dvbdev:	pointer to struct dvb_device
  */