net: phy: Log only PHY state transitions

In the current code, old and new PHY states are always logged.
>From now on, log only PHY state transitions.
Signed-off-by: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phy.c

@@ -1225,6 +1225,7 @@ void phy_state_machine(struct work_struct *work)
 	if (err < 0)
 		phy_error(phydev);
 
+	if (old_state != phydev->state)
 		phydev_dbg(phydev, "PHY state change %s -> %s\n",
 			   phy_state_to_str(old_state),
 			   phy_state_to_str(phydev->state));