Fix phy_id detection also for broken hardware.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>

--- phy_device.c.orig	2008-11-18 09:25:06.929041000 +0100
+++ phy_device.c	2008-11-18 09:27:15.876041000 +0100
@@ -227,7 +227,16 @@ struct phy_device * get_phy_device(struc
 	if (r)
 		return ERR_PTR(r);
 
-	/* If the phy_id is all Fs or all 0s, there is no device there */
+	/* If the phy_id is mostly Fs, there is no device there */
+	if ((phy_id & 0x1fffffff) == 0x1fffffff)
+		return NULL;
+
+	/*
+	 * Broken hardware is sometimes missing the pull down resistor on the
+	 * MDIO line, which results in reads to non-existent devices returning
+	 * 0 rather than 0xffff. Catch this here and treat 0 as a non-existent
+	 * device as well.
+	 */ 
 	if ((0xffff == phy_id) || (0x00 == phy_id))
 		return NULL;