Documentation: devicetree: amlogic: Document Meson GXBaby

Use "amlogic,meson-gxbb" compatible string.
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NCarlo Caione <carlo@endlessm.com>

Documentation/devicetree/bindings/arm/amlogic.txt

@@ -13,6 +13,10 @@ Boards with the Amlogic Meson8b SoC shall have the following properties:
   Required root node property:
     compatible: "amlogic,meson8b";
 
+Boards with the Amlogic Meson GXBaby SoC shall have the following properties:
+  Required root node property:
+    compatible: "amlogic,meson-gxbb";
+
 Board compatible values:
   - "geniatech,atv1200" (Meson6)
   - "minix,neo-x8" (Meson8)