ARM: dts: cubieboard4: Remove the dumb-vga-dac compatible

The dumb-vga-dac and adi,adv7123 compatibles are not supposed to be used
together according to the binding.

Since the corpro gm7123 is a drop-in replacement for the adv7123, let's
remove dumb-vga-dac from our compatible list.
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20210901091852.479202-47-maxime@cerno.tech

arch/arm/boot/dts/sun9i-a80-cubieboard4.dts

@@ -87,7 +87,7 @@ vga_con_in: endpoint {
 	};
 
 	vga-dac {
-		compatible = "corpro,gm7123", "adi,adv7123", "dumb-vga-dac";
+		compatible = "corpro,gm7123", "adi,adv7123";
 		vdd-supply = <&reg_dcdc1>;
 
 		ports {