net: dsa: mv88e6xxx: call phy_init_eee

It is safer to init the EEE before the DSA layer call
phy_ethtool_set_eee, as sf2 and qca8k are doing.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>