ethernet: use of_get_ethdev_address()

Use the new of_get_ethdev_address() helper for the cases
where dev->dev_addr is passed in directly as the destination.

  @@
  expression dev, np;
  @@
  - of_get_mac_address(np, dev->dev_addr)
  + of_get_ethdev_address(np, dev)

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>