phy: phy_ethtool_ksettings_set: Move after phy_start_aneg

This allows it to make use of a helper which assume the PHY is already
locked.

Fixes: 2d55173e ("phy: add generic function to support ksetting support")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>