dt-bindings: xlnx,vcu-settings: fix dt_binding_check warnings

When running make dt_binding_check, the xlnx,vcu-settings binding
triggers the following two warnings:

'additionalProperties' is a required property

example-0: vcu@a0041000:reg:0: [0, 2684620800, 0, 4096] is too long

Fix the binding and make the checker happy.

Signed-off-by: Michael Tretter <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/soc/xilinx/xlnx,vcu-settings.yaml

···
   - compatible
   - reg
 
+additionalProperties: false
+
 examples:
   - |
-    xlnx_vcu: vcu@a0041000 {
-          compatible = "xlnx,vcu-settings", "syscon";
-          reg = <0x0 0xa0041000 0x0 0x1000>;
+    fpga {
+        #address-cells = <2>;
+        #size-cells = <2>;
+
+        xlnx_vcu: vcu@a0041000 {
+            compatible = "xlnx,vcu-settings", "syscon";
+            reg = <0x0 0xa0041000 0x0 0x1000>;
+        };
     };
+
+...