net: phy: smsc: add LAN8742 phy support.

The current phy IDs on the available hardware.
        LAN8742 0x0007C130, 0x0007C131

Signed-off-by: Yuiko Oshino <yuiko.oshino@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>