lan743x: Add support for ethtool eeprom access

Implement ethtool eeprom access
Also provides access to OTP (One Time Programming)

Signed-off-by: Bryan Whitehead <Bryan.Whitehead@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>