arm64: dts: rockchip: Add missing secondary compatible for PX30 DSI

Add second DSI compatible to comply with DT schema validation
comming in the second patch.
Signed-off-by: David Heidelberg <david@ixit.cz>
Link: https://lore.kernel.org/r/20211211233818.88482-1-david@ixit.czSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/px30.dtsi

@@ -1072,7 +1072,7 @@ vpu_mmu: iommu@ff442800 {
 	};
 
 	dsi: dsi@ff450000 {
-		compatible = "rockchip,px30-mipi-dsi";
+		compatible = "rockchip,px30-mipi-dsi", "snps,dw-mipi-dsi";
 		reg = <0x0 0xff450000 0x0 0x10000>;
 		interrupts = <GIC_SPI 75 IRQ_TYPE_LEVEL_HIGH>;
 		clocks = <&cru PCLK_MIPI_DSI>;