netdev: netdev_priv() can now be sane again.

The private area of a netdev is now at a fixed offset once more.

Unfortunately, some assumptions that netdev_priv() == netdev->priv
crept back into the tree.  In particular this happened in the
loopback driver.  Make it use netdev->ml_priv.

Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -808,7 +808,9 @@ void dev_net_set(struct net_device *dev, struct net *net)
  */
 static inline void *netdev_priv(const struct net_device *dev)
 {
-	return dev->priv;
+	return (char *)dev + ((sizeof(struct net_device)
+			       + NETDEV_ALIGN_CONST)
+			      & ~NETDEV_ALIGN_CONST);
 }
 
 /* Set the sysfs physical device reference for the network logical device