rockchip: rk3288-veyron: Migrate "u-boot, boot0" to "u-boot, spl-boot-order"

"u-boot,spl-boot-order" is more flexible and other rockchip SoCs
has convert to use it, migrate to use the new dts property.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>

arch/arm/dts/rk3288-veyron.dtsi

@@ -16,11 +16,7 @@
 
 	chosen {
 		stdout-path = &uart2;
-	};
-
-	config {
-		u-boot,dm-pre-reloc;
-		u-boot,boot0 = &spi_flash;
+		u-boot,spl-boot-order = &spi_flash;
 	};
 
 	firmware {