net: core functions cleanup

The following functions are not used outside of net/core/dev.c
and should be declared static.

  call_netdevice_notifiers_info
  __dev_remove_offload
  netdev_has_any_upper_dev
  __netdev_adjacent_dev_remove
  __netdev_adjacent_dev_link_lists
  __netdev_adjacent_dev_unlink_lists
  __netdev_adjacent_dev_unlink
  __netdev_adjacent_dev_link_neighbour
  __netdev_adjacent_dev_unlink_neighbour

And the following are never used and should be deleted
  netdev_lower_dev_get_private_rcu
  __netdev_find_adj_rcu

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>