[POWERPC] cell: spu management xmon routines

This fixes the xmon support for the cell spu to be compatable with the split
spu platform code.

Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>