net: fec: Do not use netdev messages too early

When a valid MAC address is not found the current messages
are shown:

fec 2188000.ethernet (unnamed net_device) (uninitialized): Invalid MAC address: 00:00:00:00:00:00
fec 2188000.ethernet (unnamed net_device) (uninitialized): Using random MAC address: aa:9f:25:eb:7e:aa

Since the network device has not been registered at this point, it is better
to use dev_err()/dev_info() instead, which will provide cleaner log
messages like these:

fec 2188000.ethernet: Invalid MAC address: 00:00:00:00:00:00
fec 2188000.ethernet: Using random MAC address: aa:9f:25:eb:7e:aa

Tested on a imx6dl-pico-pi board.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>