hwmon: (fam15h_power) Refactor attributes for dynamically added

Attributes depend on the CPU model the driver gets loaded on.
Therefore, add those attributes dynamically at init time. This is more
flexible to control the different attributes on different platforms.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>