iio: chemical: add support for Aosong AGS02MA

A simple driver for the TVOC (Total Volatile Organic Compounds)
sensor from Aosong: AGS02MA

Steps in reading the VOC sensor value over i2c:
  1. Read 5 bytes from the register `AGS02MA_TVOC_READ_REG` [0x00]
  2. The first 4 bytes are taken as the big endian sensor data with final
     byte being the CRC
  3. The CRC is verified and the value is returned over an
     `IIO_CHAN_INFO_RAW` channel as percents

Tested on Raspberry Pi Zero 2W

Datasheet: https://asairsensors.com/wp-content/uploads/2021/09/AGS02MA.pdf


Signed-off-by: Anshul Dalal <anshulusr@gmail.com>
Link: https://lore.kernel.org/r/20231215162312.143568-3-anshulusr@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>