regulator: Document binding for regulator suspend voltage

This patch builds upon (291d761 regulator: Document binding for
regulator suspend state for PM state) to allow setting the uV in
addition to the state at suspend time.
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: Chris Zhong <zyw@rock-chips.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/regulator.txt

@@ -28,6 +28,8 @@ Optional properties:
 - regulator-state-[mem/disk] node has following common properties:
 	- regulator-on-in-suspend: regulator should be on in suspend state.
 	- regulator-off-in-suspend: regulator should be off in suspend state.
+	- regulator-suspend-microvolt: regulator should be set to this voltage
+	  in suspend.
 
 Deprecated properties:
 - regulator-compatible: If a regulator chip contains multiple