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

Documentation/devicetree/bindings/iio/st,st-sensors.yaml

@@ -46,6 +46,9 @@ properties:
           - st,lsm330d-accel
           - st,lsm330dl-accel
           - st,lsm330dlc-accel
+      - description: Silan Accelerometers
+        enum:
+          - silan,sc7a20
       - description: STMicroelectronics Gyroscopes
         enum:
           - st,l3g4200d-gyro