netdev: octeon_mgmt: Cleanup and modernize MAC address handling.

netdev: octeon_mgmt: Cleanup and modernize MAC address handling.

Use eth_mac_addr(), and generate a random address if none is otherwise
assigned.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
Patchwork: https://patchwork.linux-mips.org/patch/4287/
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>