dt-bindings: rng: bcm2835: add clock constraints

brcm,bcm6368-rng controllers require enabling the IPSEC clock in order to get
a functional RNG.
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/devicetree/bindings/rng/brcm,bcm2835.yaml

@@ -35,6 +35,16 @@ required:
   - compatible
   - reg
 
+if:
+  properties:
+    compatible:
+      enum:
+        - brcm,bcm6368-rng
+then:
+  required:
+    - clocks
+    - clock-names
+
 additionalProperties: false
 
 examples: