hwmon/f71805f: Add support for the Fintek F71872F/FG chip

Add support for the Fintek F71872F/FG Super-I/O chip. It is basically the
same as the Fintek F71805F/FG as far as hardware monitoring is concerned,
with two additional internal voltages monitored (VSB and battery), and 6
VID inputs (not yet supported.)

To make things a bit more confusing, two of the voltage input pins (in4
and in8) can be used for other functions. The driver reads the pin
configuration from the Super-I/O configuration space to decide whether
it must create interface files for these inputs or not.

Many thanks to Nikolay Derkach for testing the early iterations of this
code and reporting bugs.

Signed-off-by: Jean Delvare <khali@linux-fr.org>