lan78xx: Set ASD in MAC_CR when EEE is enabled.

Description:
EEE does not work with lan7800 when AutoSpeed is not set.
(This can happen when EEPROM is not populated or configured incorrectly)

Root-Cause:
When EEE is enabled, the mac config register ASD is not set
i.e. in default state, causing EEE fail.

Fix:
Set the register when eeprom is not present.

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