iio: chemical: Add driver for SEN0322

iio: chemical: Add driver for SEN0322

Add support for the DFRobot SEN0322 oxygen sensor.

To instantiate (assuming device is connected to I2C-2):
	echo 'sen0322 0x73' > /sys/class/i2c-dev/i2c-2/device/new_device

To get the oxygen concentration (assuming device is iio:device0) multiply
the values read from:
	/sys/bus/iio/devices/iio:device0/in_concentration_raw
	/sys/bus/iio/devices/iio:device0/in_concentration_scale

Datasheet: https://wiki.dfrobot.com/Gravity_I2C_Oxygen_Sensor_SKU_SEN0322
Signed-off-by: Tóth János <gomba007@gmail.com>
Link: https://patch.msgid.link/20250506-iio-chemical-sen0322-v4-2-1465ac8dc190@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>