phylib: Fix Freescale TBI PHY detection

Freescale on-chip TBI PHYs reports PHY ID as 0x0, but as of

commit 3ee82383


Author: Giulio Benetti <giulio.benetti@micronovasrl.com>
Date:   Thu Nov 13 21:53:13 2008 +0000

    phy: fix phy address bug

    PHYID returns 0xffff and not 0xffffffff when not found and in some
    case(at91sam9263) 0x0. Maybe this patch could be useful.

phy_device.c treats PHY ID == 0x0 as bogus IDs, and that results in
gianfar driver failure to see the TBI PHYs. This code snippet triggers:

	if (!priv->tbiphy) {
		printk(KERN_WARNING "SGMII mode requires that the device "
				"tree specify a tbi-handle\n");
		return;
	}

Although tbi-handle is specified in the device tree.

Btw, technically PHY ID == 0x0 is a valid ID (if we ever see a PHY
manufactured by Xerox :-).

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>