net: phy: micrel: add ksz9477_get_features()

KSZ8563R, which has same PHYID as KSZ9477 family, will change "EEE control
and capability 1" (Register 3.20) content depending on configuration of
"EEE advertisement 1" (Register 7.60). Changes on the 7.60 will affect
3.20 register.

So, instead of depending on register 3.20, driver should set supported_eee.

Proper supported_eee configuration is needed to make use of generic
PHY c45 set/get_eee functions provided by next patches.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>