dt_bindings: bd71828: Add clock output mode

The BD71828 allows configuring the clk32kout pin mode to CMOS or
open-drain. Add device-tree property for specifying the preferred mode.
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/rohm,bd71828-pmic.yaml

@@ -44,6 +44,12 @@ properties:
   clock-output-names:
     const: bd71828-32k-out
 
+  rohm,clkout-open-drain:
+    description: clk32kout mode. Set to 1 for "open-drain" or 0 for "cmos".
+    $ref: "/schemas/types.yaml#/definitions/uint32"
+    minimum: 0
+    maximum: 1
+
   rohm,charger-sense-resistor-ohms:
     minimum: 10000000
     maximum: 50000000