batman-adv: Keep interface_tx as local function

interface_tx is not used outside of soft-interface.c and thus doesn't
need to be declared inside soft-interface.h
Signed-off-by: Sven Eckelmann <sven@narfation.org>

net/batman-adv/soft-interface.c

@@ -553,7 +553,7 @@ static int interface_change_mtu(struct net_device *dev, int new_mtu)
 	return 0;
 }
 
-int interface_tx(struct sk_buff *skb, struct net_device *soft_iface)
+static int interface_tx(struct sk_buff *skb, struct net_device *soft_iface)
 {
 	struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
 	struct bat_priv *bat_priv = netdev_priv(soft_iface);

net/batman-adv/soft-interface.h

@@ -25,7 +25,6 @@
 int my_skb_head_push(struct sk_buff *skb, unsigned int len);
 int softif_neigh_seq_print_text(struct seq_file *seq, void *offset);
 void softif_neigh_purge(struct bat_priv *bat_priv);
-int interface_tx(struct sk_buff *skb, struct net_device *soft_iface);
 void interface_rx(struct net_device *soft_iface,
 		  struct sk_buff *skb, struct hard_iface *recv_if,
 		  int hdr_size);