phylib: don't return NULL from get_phy_device()

Arnd Bergmann asked that get_phy_device() returns either NULL or the error
value,  not both on error.  Do as he said, return ERR_PTR(-ENODEV) instead
of NULL when the PHY ID registers read as  all ones.
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phy_device.c

@@ -529,7 +529,7 @@ struct phy_device *get_phy_device(struct mii_bus *bus, int addr, bool is_c45)
 
 	/* If the phy_id is mostly Fs, there is no device there */
 	if ((phy_id & 0x1fffffff) == 0x1fffffff)
-		return NULL;
+		return ERR_PTR(-ENODEV);
 
 	return phy_device_create(bus, addr, phy_id, is_c45, &c45_ids);
 }