bond: track sum of rx_nohandler for all slaves

Sample output with this set applied for an active-backup bond:

$ cat /sys/devices/virtual/net/bond0/lower_p7p1/statistics/rx_nohandler
16568
$ cat /sys/devices/virtual/net/bond0/lower_p5p2/statistics/rx_nohandler
16583
$ cat /sys/devices/virtual/net/bond0/statistics/rx_nohandler
33151

CC: Jay Vosburgh <j.vosburgh@gmail.com>
CC: Veaceslav Falico <vfalico@gmail.com>
CC: Andy Gospodarek <gospo@cumulusnetworks.com>
CC: netdev@vger.kernel.org
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -3309,6 +3309,7 @@ static struct rtnl_link_stats64 *bond_get_stats(struct net_device *bond_dev,
 		stats->rx_bytes += sstats->rx_bytes - pstats->rx_bytes;
 		stats->rx_errors += sstats->rx_errors - pstats->rx_errors;
 		stats->rx_dropped += sstats->rx_dropped - pstats->rx_dropped;
+		stats->rx_nohandler += sstats->rx_nohandler - pstats->rx_nohandler;
 
 		stats->tx_packets += sstats->tx_packets - pstats->tx_packets;;
 		stats->tx_bytes += sstats->tx_bytes - pstats->tx_bytes;