net: phy: mscc: Add EEE init sequence

Microsemi PHYs (VSC 8530/31/40/41) need to update the Energy Efficient
Ethernet initialization sequence.
In order to avoid certain link state errors that could result in link
drops and packet loss, the physical coding sublayer (PCS) must be
updated with settings related to EEE in order to improve performance.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Raju Lakkaraju <Raju.Lakkaraju@microchip.com>
Signed-off-by: Quentin Schulz <quentin.schulz@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>