mac802154: add get short address method

Add method to get the device short 802.15.4 address. This call
needed by ieee802154 layer to satisfy 'iz list' request from
the user space.

Signed-off-by: Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/mac802154/mib.c b/net/mac802154/mib.c
index 380829d..5c66b8f 100644
--- a/net/mac802154/mib.c
+++ b/net/mac802154/mib.c
@@ -100,6 +100,20 @@
 	}
 }
 
+u16 mac802154_dev_get_short_addr(const struct net_device *dev)
+{
+	struct mac802154_sub_if_data *priv = netdev_priv(dev);
+	u16 ret;
+
+	BUG_ON(dev->type != ARPHRD_IEEE802154);
+
+	spin_lock_bh(&priv->mib_lock);
+	ret = priv->short_addr;
+	spin_unlock_bh(&priv->mib_lock);
+
+	return ret;
+}
+
 void mac802154_dev_set_ieee_addr(struct net_device *dev)
 {
 	struct mac802154_sub_if_data *priv = netdev_priv(dev);