octeon: convert to use netdev_for_each_mc_addr

Hmm so actually my original patch including this bit was correct,
"list = list->next;" confused me :) - will send patch correcting that in a few.

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>