In 5.4 kernel old u32 array way of setting network features was dropped and linkmode is now the only way.
So lets migrate the PHY driver to support linkmode.
Also, now in order for gigabit to work, PHY driver needs to advertise PHY_GBIT_FEATURES instead of PHY_BASIC_FEATURES
Signed-off-by: Robert Marko <robert.marko@sartura.hr>