net/ipv4/ipconfig: add device address to a KERN_INFO message

adds a "hwaddr" to the "IP-Config: Complete" KERN_INFO message
with the dev_addr of the device selected for auto configuration.

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>