Currently reset and powerdown are not implemented on the Maple board,
and attempting to do so will (incorrectly return).  This implements
the proper communication with the service processor, allowing correct
reset and powerdown on the Maple board, by communicating with the
service processor.  If somehow it's unable to communicate with the
service processor it will loop forever instead.

Note that powerdown on the Maple will power down the CPUs, but not the
fans or other board components due to hardware and firmware
limitations.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Frank Rowand <frowand@mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>