iio: st-sensors: Update ST Sensor bindings

This adjusts the ST Sensor bindings with the more fine-grained
syntax checks that were proposed late in the last kernel cycle
and colliding with parallel work.

Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20210412122331.1631643-1-linus.walleij@linaro.org


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