hwmon: (sht3x) read out sensor serial number

hwmon: (sht3x) read out sensor serial number

The temperature/humidity sensors of the STS3x/SHT3x family are
calibrated and factory-programmed with a unique serial number.
For some sensors, this serial number can be used to obtain a calibration
certificate via an API provided by the manufacturer (Sensirion).
Expose the serial number via debugfs.

Tested with: 2x STS31, 1x STS32, 1x SHT31

Signed-off-by: Stefan Gloor <code@stefan-gloor.ch>
Link: https://lore.kernel.org/r/20240131111512.25321-2-code@stefan-gloor.ch
Signed-off-by: Guenter Roeck <linux@roeck-us.net>