netpoll: copy dev name of slaves to struct netpoll

Otherwise we will not see the name of the slave dev in error
message:

[  388.469446] (null):  doesn't support polling, aborting.

Signed-off-by: WANG Cong <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 652b30e..eafe44a 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1297,6 +1297,7 @@
 		goto out;
 
 	np->dev = slave->dev;
+	strlcpy(np->dev_name, slave->dev->name, IFNAMSIZ);
 	err = __netpoll_setup(np);
 	if (err) {
 		kfree(np);