lan78xx: Use default values loaded from EEPROM/OTP after reset

Use default value of auto duplex and auto speed values loaded
from EEPROM/OTP after reset. The LAN78xx allows platform
configurations to be loaded from EEPROM/OTP.
Ex: When external phy is connected, the MAC can be configured to
have correct auto speed, auto duplex, auto polarity configured
from the EEPROM/OTP.

Fixes: 55d7de9d ("Microchip's LAN7800 family USB 2/3 to 10/100/1000 Ethernet device driver")
Signed-off-by: Nisar Sayed <Nisar.Sayed@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>