hwmon: Add driver for AMD family 15h processor power information

This CPU family provides NB register values to gather following
TDP information

* ProcessorPwrWatts: Specifies in Watts the maximum amount of power
  the processor can support.
* CurrPwrWatts: Specifies in Watts the current amount of power being
  consumed by the processor.

This driver provides

* power1_crit (ProcessorPwrWatts)
* power1_input (CurrPwrWatts)

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>