hwmon: Add AHT10 Temperature and Humidity Sensor Driver

This patch adds a hwmon driver for the AHT10 Temperature and
Humidity sensor. It has a maximum sample rate, as the datasheet
states that the chip may heat up if it is sampled more than once
every two seconds.

Has been tested a to work on a raspberrypi0w

Signed-off-by: Johannes Cornelis Draaijer (datdenkikniet) <jcdra1@gmail.com>
Link: https://lore.kernel.org/r/20210107194014.GA88780@desktop
[groeck: dropped AHT10_ADDR (unused) and use AHT10_MEAS_SIZE where
 appropriate; dropped change log]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>