[POWERPC] ps3: add OS params support

Adds support for early access to the parameter data from the PS3 'Other OS'
flash memory area.  The parameter data mainly holds user preferences like
static ip address.

Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>