dt-bindings: iio: magnetometer: add ti tmag5273 documentation file

Add bindings for TI TMAG5273.

Signed-off-by: Gerald Loacker <gerald.loacker@wolfvision.net>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221201072220.402585-3-gerald.loacker@wolfvision.net


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