In order to enable and use USB/OHCI on the MPC5200 the USB PLL register must be
set.

It's not easy to find a correct value for this register, it seems it depends on
the used external reference frequency and some other 'magic' things. There are
some values out in the wild for the 33,333333 MHz and 33,333000 MHz reference
frequency case, but they are not consistent over the boards.

The value used here in this change for the USB PLL register is from the first
days of support for this platform and works at least on the reference
baseboard.

Signed-off-by: Juergen Borleis <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>