dt-bindings: arm: realtek: Document MeLE V9

Define a compatible string for MeLE V9 Media Player.

Cc: meleservice@mele.cn
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>

Documentation/devicetree/bindings/arm/realtek.txt

@@ -12,6 +12,7 @@ Required root node properties:
 
 Root node property compatible must contain, depending on board:
 
+ - MeLE V9: "mele,v9"
  - ProBox2 AVA: "probox2,ava"
  - Zidoo X9S: "zidoo,x9s"