net: phy: fix phy link up when limiting speed via device tree

commit eb686231 upstream.

When limiting phy link speed using "max-speed" to 100mbps or less on a
giga bit phy, phy never completes auto negotiation and phy state
machine is held in PHY_AN. Fixing this issue by comparing the giga
bit advertise though phydev->supported doesn't have it but phy has
BMSR_ESTATEN set. So that auto negotiation is restarted as old and
new advertise are different and link comes up fine.
Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/net/phy/phy_device.c

@@ -780,9 +780,10 @@ static int genphy_config_advert(struct phy_device *phydev)
 	if (phydev->supported & (SUPPORTED_1000baseT_Half |
 				 SUPPORTED_1000baseT_Full)) {
 		adv |= ethtool_adv_to_mii_ctrl1000_t(advertise);
+	}
+
 	if (adv != oldadv)
 		changed = 1;
-	}
 
 	err = phy_write(phydev, MII_CTRL1000, adv);
 	if (err < 0)