[CELL] saving spus information for kexec crash

This patch adds support for investigating spus information after a
kernel crash event, through kdump vmcore file.
Implementation is based on xmon code, but the new functionality was
kept independent from xmon.

Signed-off-by: Lucio Jose Herculano Correia <luciojhc@br.ibm.com>
Signed-off-by: Andre Detsch <adetsch@br.ibm.com>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>