net: phy: marvell: Show complete link partner advertising

Give back all modes advertised by the link partner. This change brings
the marvell phy driver in line with all other phy drivers.

Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>