dt-bindings: iio: humidity: add ENS210 sensor family

Add device tree documentation for ENS210 family of temperature and
humidity sensors

Signed-off-by: Joshua Felmeden <jfelmeden@thegoodpenguin.co.uk>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20240805-ens21x-v6-1-5bb576ef26a6@thegoodpenguin.co.uk


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