hwmon: (pmbus) cffps: Add debugfs entries

hwmon: (pmbus) cffps: Add debugfs entries

Add debugfs entries for additional power supply data, including part
number, serial number, FRU number, firmware revision, ccin, and the
input history of the power supply. The input history is 10 minutes of
input power data in the form of twenty 30-second packets. Each packet
contains average and maximum power for that 30 second period.

Signed-off-by: Edward A. James <eajames@us.ibm.com>
[groeck: Fixed endianness problem]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>