batman-adv: fix batadv_interface_tx()'s return type

The method ndo_start_xmit() is defined as returning an 'netdev_tx_t',
which is a typedef for an enum type, but the implementation in this
driver returns an 'int'.

Fix this by returning 'netdev_tx_t' in this driver too.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
[sven@narfation.org: fixed alignment]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

net/batman-adv/soft-interface.c

@@ -188,7 +188,7 @@ static void batadv_interface_set_rx_mode(struct net_device *dev)
 {
 }
 
-static int batadv_interface_tx(struct sk_buff *skb,
+static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
 				       struct net_device *soft_iface)
 {
 	struct ethhdr *ethhdr;