dt-bindings: ili9881c: add rotation property

Allow the standard rotation property from panel-common for ILI9881C
based panels.
Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211020153432.383845-3-john@metanate.com

Documentation/devicetree/bindings/display/panel/ilitek,ili9881c.yaml

@@ -25,6 +25,7 @@ properties:
   power-supply: true
   reg: true
   reset-gpios: true
+  rotation: true
 
 required:
   - compatible