[POWERPC] 85xx: mpc8568mds - update dts to be able to use UCCs

1. UCC1's RX_DV pin is 16, not 15;
2. UCC1's phy is at 0x7, not 0x1. Schematics says 0x7, and recent
   u-boot also using 0x7.
3. Use gianfar's (eTSEC) mdio bus. This is hardware default setup.
4. tx-clock should be CLK16 (GE125, PB31);
5. phy-connection-type is RGMII-ID;

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>