dt-bindings: bus: Drop empty compatible string in example

In preparation to add generic checks of compatible strings, drop
the compatible as '...' is not a valid compatible string.

Cc: Maxime Ripard <mripard@kernel.org>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Rob Herring <robh@kernel.org>

Author: robherring

Documentation/devicetree/bindings/bus/allwinner,sun8i-a23-rsb.yaml

@@ -70,7 +70,6 @@ examples:
         #size-cells = <0>;
 
         pmic@3e3 {
-            compatible = "...";
             reg = <0x3e3>;
 
             /* ... */