dt-bindings: reset: hisilicon: Update compatible documentation

The reset driver now supports the ao reset controller, so update the
documentation to match.

Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: dri-devel@lists.freedesktop.org
Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/reset/hisilicon,hi6220-reset.txt

@@ -11,6 +11,7 @@ Required properties:
 - compatible: should be one of the following:
   - "hisilicon,hi6220-sysctrl", "syscon" : For peripheral reset controller.
   - "hisilicon,hi6220-mediactrl", "syscon" : For media reset controller.
+  - "hisilicon,hi6220-aoctrl", "syscon" : For ao reset controller.
 - reg: should be register base and length as documented in the
   datasheet
 - #reset-cells: 1, see below