[media] media-devnode: move kernel-doc documentation to the header

As we're using the headers file only for documentation, move the
two kernel-doc macros to the header, and fix it to avoid
warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/media-devnode.c

@@ -217,20 +217,6 @@ static const struct file_operations media_devnode_fops = {
 	.llseek = no_llseek,
 };
 
-/**
- * media_devnode_register - register a media device node
- * @mdev: media device node structure we want to register
- *
- * The registration code assigns minor numbers and registers the new device node
- * with the kernel. An error is returned if no free minor number can be found,
- * or if the registration of the device node fails.
- *
- * Zero is returned on success.
- *
- * Note that if the media_devnode_register call fails, the release() callback of
- * the media_devnode structure is *not* called, so the caller is responsible for
- * freeing any data.
- */
 int __must_check media_devnode_register(struct media_devnode *mdev,
 					struct module *owner)
 {
@@ -285,16 +271,6 @@ int __must_check media_devnode_register(struct media_devnode *mdev,
 	return ret;
 }
 
-/**
- * media_devnode_unregister - unregister a media device node
- * @mdev: the device node to unregister
- *
- * This unregisters the passed device. Future open calls will be met with
- * errors.
- *
- * This function can safely be called if the device node has never been
- * registered or has already been unregistered.
- */
 void media_devnode_unregister(struct media_devnode *mdev)
 {
 	/* Check if mdev was ever registered at all */

include/media/media-devnode.h

@@ -86,8 +86,35 @@ struct media_devnode {
 /* dev to media_devnode */
 #define to_media_devnode(cd) container_of(cd, struct media_devnode, dev)
 
+/**
+ * media_devnode_register - register a media device node
+ *
+ * @mdev: media device node structure we want to register
+ * @owner: should be filled with %THIS_MODULE
+ *
+ * The registration code assigns minor numbers and registers the new device node
+ * with the kernel. An error is returned if no free minor number can be found,
+ * or if the registration of the device node fails.
+ *
+ * Zero is returned on success.
+ *
+ * Note that if the media_devnode_register call fails, the release() callback of
+ * the media_devnode structure is *not* called, so the caller is responsible for
+ * freeing any data.
+ */
 int __must_check media_devnode_register(struct media_devnode *mdev,
 					struct module *owner);
+
+/**
+ * media_devnode_unregister - unregister a media device node
+ * @mdev: the device node to unregister
+ *
+ * This unregisters the passed device. Future open calls will be met with
+ * errors.
+ *
+ * This function can safely be called if the device node has never been
+ * registered or has already been unregistered.
+ */
 void media_devnode_unregister(struct media_devnode *mdev);
 
 static inline struct media_devnode *media_devnode_data(struct file *filp)