bonding: disable netpoll on enslave failure

slave_disable_netpoll() is not called upon enslave failure which would
lead to a memory leak. Call slave_disable_netpoll() after err_detach as
that's the first error path after enabling netpoll on that slave.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -1920,6 +1920,7 @@ err_detach:
 		write_unlock_bh(&bond->curr_slave_lock);
 		read_unlock(&bond->lock);
 	}
+	slave_disable_netpoll(new_slave);
 
 err_close:
 	slave_dev->priv_flags &= ~IFF_BONDING;