net: of_mdio: fix of_set_phy_supported after driver probing

Commit 8fdade4b ("net: of_mdio: parse "max-speed" property to set PHY
supported features") introduced a typo in of_set_phy_supported for the
first assignment of phydev->supported which will not effectively limit
the PHY device supported features bits if the PHY driver contains
"higher" features (e.g: max-speed = <100> and PHY driver has
PHY_GBIT_FEATURES set).

Fix this by making sure that the very first thing is to reset to sane
defaults (PHY_BASIC_FEATURES) and then progressively add speed features
as we parse them.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/of/of_mdio.c

@@ -24,7 +24,11 @@ MODULE_LICENSE("GPL");
 
 static void of_set_phy_supported(struct phy_device *phydev, u32 max_speed)
 {
-	phydev->supported |= PHY_DEFAULT_FEATURES;
+	/* The default values for phydev->supported are provided by the PHY
+	 * driver "features" member, we want to reset to sane defaults fist
+	 * before supporting higher speeds.
+	 */
+	phydev->supported &= PHY_DEFAULT_FEATURES;
 
 	switch (max_speed) {
 	default: