net: fix kdoc on __dev_queue_xmit()

Commit c526fd8f ("net: inline dev_queue_xmit()") exported
__dev_queue_xmit(), now it's being rendered in html docs, triggering:

Documentation/networking/kapi:92: net/core/dev.c:4101: WARNING: Missing matching underline for section title overline.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/linux-next/20220503073420.6d3f135d@canb.auug.org.au/
Fixes: c526fd8f ("net: inline dev_queue_xmit()")
Link: https://lore.kernel.org/r/20220509170412.1069190-1-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/dev.c

@@ -4131,7 +4131,7 @@ struct netdev_queue *netdev_core_pick_tx(struct net_device *dev,
 }
 
 /**
- *	__dev_queue_xmit - transmit a buffer
+ * __dev_queue_xmit() - transmit a buffer
  * @skb:	buffer to transmit
  * @sb_dev:	suboordinate device used for L2 forwarding offload
  *
@@ -4139,22 +4139,17 @@ struct netdev_queue *netdev_core_pick_tx(struct net_device *dev,
  * have set the device and priority and built the buffer before calling
  * this function. The function can be called from an interrupt.
  *
- *	A negative errno code is returned on a failure. A success does not
- *	guarantee the frame will be transmitted as it may be dropped due
- *	to congestion or traffic shaping.
- *
- * -----------------------------------------------------------------------------------
- *      I notice this method can also return errors from the queue disciplines,
- *      including NET_XMIT_DROP, which is a positive value.  So, errors can also
- *      be positive.
+ * When calling this method, interrupts MUST be enabled. This is because
+ * the BH enable code must have IRQs enabled so that it will not deadlock.
  *
  * Regardless of the return value, the skb is consumed, so it is currently
  * difficult to retry a send to this method. (You can bump the ref count
  * before sending to hold a reference for retry if you are careful.)
  *
- *      When calling this method, interrupts MUST be enabled.  This is because
- *      the BH enable code must have IRQs enabled so that it will not deadlock.
- *          --BLG
+ * Return:
+ * * 0				- buffer successfully transmitted
+ * * positive qdisc return code	- NET_XMIT_DROP etc.
+ * * negative errno		- other errors
  */
 int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
 {