dt-bindings: display: novatek, nt36672a: add backlight property

Add backlight property and update example to include it.
Signed-off-by: Joel Selvaraj <jo@jsfamily.in>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/BY5PR02MB70090BB5D8C7D655BEE0642FD9E09@BY5PR02MB7009.namprd02.prod.outlook.com

Documentation/devicetree/bindings/display/panel/novatek,nt36672a.yaml

@@ -46,6 +46,7 @@ properties:
 
   reg: true
   port: true
+  backlight: true
 
 required:
   - compatible
@@ -73,6 +74,7 @@ examples:
             vddpos-supply = <&lab>;
             vddneg-supply = <&ibb>;
 
+            backlight = <&pmi8998_wled>;
             reset-gpios = <&tlmm 6 GPIO_ACTIVE_HIGH>;
 
             port {