Marvell phy: check link status in case of fiber link.

For concerned phy, the fiber link is checked before the copper link.
According to datasheet, the link which is up is enabled.

If both links are down, copper link would be used.
To detect fiber link status, we used the real time status
because of troubles with the copper method.

Tested with Marvell 88E1512.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Charles-Antoine Couret <charles-antoine.couret@nexvision.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>