mac80211: fix description comment of ieee80211_subif_start_xmit

The function description claimed that on error the skb isn't
freed even though it is, and stated return values that are
different than what really happens in the code.
Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tx.c

@@ -1789,9 +1789,8 @@ static void ieee80211_tx_latency_start_msrmnt(struct ieee80211_local *local,
  * @skb: packet to be sent
  * @dev: incoming interface
  *
- * Returns: 0 on success (and frees skb in this case) or 1 on failure (skb will
- * not be freed, and caller is responsible for either retrying later or freeing
- * skb).
+ * Returns: NETDEV_TX_OK both on success and on failure. On failure skb will
+ *	be freed.
  *
  * This function takes in an Ethernet header and encapsulates it with suitable
  * IEEE 802.11 header based on which interface the packet is coming in. The