xen-netfront: fix xennet_start_xmit()'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: NLuc Van Oostenryck <luc.vanoostenryck@gmail.com>
Reviewed-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NJuergen Gross <jgross@suse.com>

drivers/net/xen-netfront.c

@@ -564,7 +564,7 @@ static u16 xennet_select_queue(struct net_device *dev, struct sk_buff *skb,
 
 #define MAX_XEN_SKB_FRAGS (65536 / XEN_PAGE_SIZE + 1)
 
-static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct netfront_info *np = netdev_priv(dev);
 	struct netfront_stats *tx_stats = this_cpu_ptr(np->tx_stats);