net: ethoc: Use ether_addr_copy()

Use ether_addr_copy() instead of memcpy() to set netdev->dev_addr (which
is 2-byte aligned).

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Reviewed-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>