[POWERPC] spu_manage: Use newer physical-id attribute

Legacy device tree used the reg property for the physical id of an
spe.  On newer device tree layouts the reg property contains the
"correct" value in the reg attribute.  So there has been intoduced the
"physical-id" on newer devicetree layouts.  The id is stored by
spu_manage into the spu struct as spe_id.  cbe_thermal has been
changed to use the spu->spe_id.  There's no need for the thermal code
to check devicetree attributes for itself.

Signed-off-by: Christian Krafft <krafft@de.ibm.com>
Cc: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>