net: core: Fix kernel-doc for netdev_upper_link()

Fixes the following warnings:
./net/core/dev.c:6438: warning: No description found for parameter 'extack'
./net/core/dev.c:6461: warning: No description found for parameter 'extack'

Fixes: 42ab19ee ("net: Add extack to upper device linking")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -6424,6 +6424,7 @@ static int __netdev_upper_dev_link(struct net_device *dev,
  * netdev_upper_dev_link - Add a link to the upper device
  * @dev: device
  * @upper_dev: new upper device
+ * @extack: netlink extended ack
  *
  * Adds a link to device which is upper to this one. The caller must hold
  * the RTNL lock. On a failure a negative errno code is returned.
@@ -6445,6 +6446,7 @@ EXPORT_SYMBOL(netdev_upper_dev_link);
  * @upper_dev: new upper device
  * @upper_priv: upper device private
  * @upper_info: upper info to be passed down via notifier
+ * @extack: netlink extended ack
  *
  * Adds a link to device which is upper to this one. In this case, only
  * one master upper device can be linked, although other non-master devices