[NET]: move dev_mc_discard from dev_mcast.c to dev.c

Because this function is only called by unregister_netdevice,
this moving could make this non-global function static,
and also remove its declaration in netdevice.h;

Any further, function __dev_addr_discard is also just called by
dev_mc_discard and dev_unicast_discard, keeping this two functions
both in one c file could make __dev_addr_discard also static
and remove its declaration in netdevice.h;

Futhermore, the sequential call to dev_unicast_discard and then
dev_mc_discard in unregister_netdevice have a similar mechanism that:
(netif_tx_lock_bh / __dev_addr_discard / netif_tx_unlock_bh),
they should merged into one to eliminate duplicates in acquiring and
releasing the dev->_xmit_lock, this would be done in my following patch.

Signed-off-by: Denis Cheng <crquan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1098,10 +1098,8 @@ extern int 		dev_mc_delete(struct net_device *dev, void *addr, int alen, int all
 extern int		dev_mc_add(struct net_device *dev, void *addr, int alen, int newonly);
 extern int		dev_mc_sync(struct net_device *to, struct net_device *from);
 extern void		dev_mc_unsync(struct net_device *to, struct net_device *from);
-extern void		dev_mc_discard(struct net_device *dev);
 extern int 		__dev_addr_delete(struct dev_addr_list **list, int *count, void *addr, int alen, int all);
 extern int		__dev_addr_add(struct dev_addr_list **list, int *count, void *addr, int alen, int newonly);
-extern void		__dev_addr_discard(struct dev_addr_list **list);
 extern void		dev_set_promiscuity(struct net_device *dev, int inc);
 extern void		dev_set_allmulti(struct net_device *dev, int inc);
 extern void		netdev_state_change(struct net_device *dev);

net/core/dev.c

@@ -2715,7 +2715,7 @@ int __dev_addr_add(struct dev_addr_list **list, int *count,
 	return 0;
 }
 
-void __dev_addr_discard(struct dev_addr_list **list)
+static void __dev_addr_discard(struct dev_addr_list **list)
 {
 	struct dev_addr_list *tmp;
 
@@ -2785,6 +2785,18 @@ static void dev_unicast_discard(struct net_device *dev)
 	netif_tx_unlock_bh(dev);
 }
 
+/*
+ *	Discard multicast list when a device is downed
+ */
+
+static void dev_mc_discard(struct net_device *dev)
+{
+	netif_tx_lock_bh(dev);
+	__dev_addr_discard(&dev->mc_list);
+	dev->mc_count = 0;
+	netif_tx_unlock_bh(dev);
+}
+
 unsigned dev_get_flags(const struct net_device *dev)
 {
 	unsigned flags;

net/core/dev_mcast.c

@@ -177,18 +177,6 @@ void dev_mc_unsync(struct net_device *to, struct net_device *from)
 }
 EXPORT_SYMBOL(dev_mc_unsync);
 
-/*
- *	Discard multicast list when a device is downed
- */
-
-void dev_mc_discard(struct net_device *dev)
-{
-	netif_tx_lock_bh(dev);
-	__dev_addr_discard(&dev->mc_list);
-	dev->mc_count = 0;
-	netif_tx_unlock_bh(dev);
-}
-
 #ifdef CONFIG_PROC_FS
 static void *dev_mc_seq_start(struct seq_file *seq, loff_t *pos)
 {