hwmon: (it87) Add support for IT8792E

The chip is similar to IT8732E, but supports only three fans
and pwm outputs instead of four (the driver currently does not
support the 4th fan and pwm output of IT8732E).

Note that the chip ID is 0x8733, not 0x8792 as one would expect.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>