net: phy: marvell: Enable interrupt function on LED2 pin

The LED2[2]/INTn pin on Marvell 88E1318S as well as 88E1510/12/14/18 needs
to be configured to be usable as interrupt not only when WOL is enabled,
but whenever we rely on interrupts from the PHY.

Signed-off-by: Esben Haabendal <eha@deif.com>
Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>