dts/mpc8569mds: Cleanup tbi phy to support rtbi

After these change, when need to work in rtbi mode,
just change phy-connection-type to "rtbi".

Also, this work can be done by u-boot.

Signed-off-by: Liu Yu <yu.liu@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>