net: dsa: call phy_init_eee in DSA layer

All DSA drivers are calling phy_init_eee if eee_enabled is true.

Move up this statement in the DSA layer to simplify the DSA drivers.
qca8k does not require to cache the ethtool_eee structures from now on.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>