dt-bindings: iio: accel: Add required regulators to bma180

The bma180 and related chips should have two regulators attached to
them.  The IIO driver currently uses them, document them here as
well.
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/accel/bma180.txt

@@ -14,6 +14,8 @@ Required properties:
     "bosch,bma254"
     "bosch,smb380"
   - reg : the I2C address of the sensor
+  - vdd-supply : regulator phandle connected to the VDD pin
+  - vddio-supply : regulator phandle connected to the VDDIO pin
 
 Optional properties: