[POWERPC] cell: add temperature to SPU and CPU sysfs entries

This patch adds a module that registers sysfs attributes to CPU and SPU
containing the temperature of the CBE.

They can be found under
/sys/devices/system/spu/cpuX/thermal/temperature[0|1]
/sys/devices/system/spu/spuX/thermal/temperature

The temperature is read from the on-chip temperature sensors.

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