powerpc/85xx: Don't scan for TBI PHY addresses on MPC8569E-MDS boards

Sometimes (e.g. when there are no UEMs attached to a board)
fsl_pq_mdio_find_free() fails to find a spare address for a TBI PHY,
this is because get_phy_id() returns bogus 0x0000ffff values
(0xffffffff is expected), and therefore mdio bus probing fails with
the following message:

  fsl-pq_mdio: probe of e0082120.mdio failed with error -16

And obviously ethernet doesn't work after this.

This patch solves the problem by adding tbi-phy node into mdio node,
so that we won't scan for spare addresses, we'll just use a fixed one.
Signed-off-by: NAnton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

arch/powerpc/boot/dts/mpc8569mds.dts

@@ -501,6 +501,10 @@ qe_phy7: ethernet-phy@06 {
 				reg = <0x6>;
 				device_type = "ethernet-phy";
 			};
+			tbi-phy@11 {
+				reg = <0x11>;
+				device_type = "tbi-phy";
+			};
 		};
 		mdio@3520 {
 			#address-cells = <1>;