dt-bindings: display: arm: versatile: Pass the sysreg unit name

Pass the sysreg unit name to fix the following warning seen with
'make dt_binding_check':

Warning (unit_address_vs_reg): /example-0/sysreg: node has a reg or ranges property, but no unit name
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20200629215500.18037-1-festevam@gmail.comSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/display/panel/arm,versatile-tft-panel.yaml

@@ -33,7 +33,7 @@ additionalProperties: false
 
 examples:
   - |
-    sysreg {
+    sysreg@0 {
         compatible = "arm,versatile-sysreg", "syscon", "simple-mfd";
         reg = <0x00000 0x1000>;