dt-bindings: iio: st: Add Silan SC7A20 accelerometer

This chip is not an ST part, but it appears to be register-compatible
with the LIS2DH, so it can use the same binding.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20220202235049.8051-3-samuel@sholland.org


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