net: fix a leak in register_netdevice()

We have to free "dev->name_node" on this error path.

Fixes: ff927412 ("net: introduce name_node struct to be used in hashlist")
Reported-by:  <syzbot+6e13e65ffbaa33757bcb@syzkaller.appspotmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>