[AFS]: Replace rtnetlink client by direct dev_base walking

Replace the large and complicated rtnetlink client by two simple
functions for getting the MAC address for the first ethernet device
and building a list of IPv4 addresses.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>