hwmon: Add NPCM7xx PWM and Fan driver

Add Nuvoton BMC NPCM750/730/715/705 Pulse Width Modulation (PWM)
and Fan tacho driver.

The Nuvoton BMC NPCM750/730/715/705 supports 8 PWM controller outputs
and 16 Fan controller inputs.

The driver provides a sysfs entries through which the user can
configure the duty-cycle value from 0(off) and 255(full speed)
and read the fan tacho rpm value.

Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>