hwmon: (fam15h_power) Make actual power reporting conditional

power1_input should only be reported for Fam15h, Models 00h-0fh
So, introduce a is_visible function to take care of this.

As suggested by Guenter here:
http://marc.info/?l=linux-kernel&m=141038145616437&w=2

Suggested-by: Guenter Roeck <linux@roeck-us.net>
Fixes: 22e32f4f5777 ('x86,AMD: Power driver support for AMD's family 16h processors')
Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>