ucc_geth: Fix the wrong the Rx/Tx FIFO size

current the Rx/Tx FIFO size settings cause problem
when four UEC ethernets work simultaneously.

eg: GETH1, UEM-J15, GETH2, UEC-J5 on 8569MDS board

 $ ifconfig eth0 10.193.20.166
 $ ifconfig eth1 10.193.20.167
 $ ifconfig eth2 10.193.20.168
 then
 $ ifconfig eth3 10.193.20.169

The fourth ethernet will cause all of interface broken,
you cann't ping successfully any more.
The patch fix this issue for MPC8569 Rev1.0 and Rev2.0

Signed-off-by: Dave Liu <daveliu@freescale.com>
Acked-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>