can: add the missing netlink get_xstats_size callback

This patch adds the missing "get_xstats_size" callback for the
netlink interface, which is required if "fill_xstats" is used,
as pointed out by Patrick McHardy.
Signed-off-by: NWolfgang Grandegger <wg@grandegger.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/can/dev.c

@@ -629,6 +629,11 @@ static int can_fill_info(struct sk_buff *skb, const struct net_device *dev)
 	return -EMSGSIZE;
 }
 
+static size_t can_get_xstats_size(const struct net_device *dev)
+{
+	return sizeof(struct can_device_stats);
+}
+
 static int can_fill_xstats(struct sk_buff *skb, const struct net_device *dev)
 {
 	struct can_priv *priv = netdev_priv(dev);
@@ -657,6 +662,7 @@ static struct rtnl_link_ops can_link_ops __read_mostly = {
 	.changelink	= can_changelink,
 	.get_size	= can_get_size,
 	.fill_info	= can_fill_info,
+	.get_xstats_size = can_get_xstats_size,
 	.fill_xstats	= can_fill_xstats,
 };