DM9000: Allow randomised ethernet address

Allow randomised ethernet address if the device does not have a valid
EEPROM or pre-set MAC address.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: David S. Miller <davem@davemloft.net>