NET: Fix MAC addr handling for smc911x

NET: Fix MAC addr handling for smc911x

This patch turns off MAC address mismatch warning when
optional eeprom programmed with MAC address is not available.
In that case, smc911x's MAC address register has its default
value ff:ff:ff:ff:ff:ff and it's not a valid address. This
makes eth_initialize() show the warning which has no
meaningful information while environment variable ethaddr
overrides the address read from the register. If there's no
eeprom and the value of MAC address register is not valid
after initialization, dev->enetaddr had better not be updated
and maintain its initial value 00:00:00:00:00:00, which I
think is what eth_initialize() expects. This is not a bug fix.
Even without this patch, the driver works fine. It's just for
enhancing the way of displaying messages.

Signed-off-by: Seunghyeon Rhee <seunghyeon@lpmtec.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>