dt-bindings: watchdog: sun4i: Add the watchdog clock

The Allwinner watchdog has a clock that has been described in some DT, but
not all of them.

The binding is also completely missing that description. Let's add that
property to be consistent.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190821143835.7294-4-mripard@kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Documentation/devicetree/bindings/watchdog/allwinner,sun4i-a10-wdt.yaml

@@ -31,12 +31,16 @@ properties:
   reg:
     maxItems: 1
 
+  clocks:
+    maxItems: 1
+
   interrupts:
     maxItems: 1
 
 required:
   - compatible
   - reg
+  - clocks
   - interrupts
 
 unevaluatedProperties: false
@@ -47,6 +51,7 @@ examples:
         compatible = "allwinner,sun4i-a10-wdt";
         reg = <0x01c20c90 0x10>;
         interrupts = <24>;
+        clocks = <&osc24M>;
         timeout-sec = <10>;
     };