rockchip: dts: rk3399-firefly: move u-boot, spl-boot-order to to the u-boot.dtsi

The u-boot specific device tree directives should be in u-boot.dtsi
Signed-off-by: NPeter Robinson <pbrobinson@gmail.com>
Reviewed-by: NKever Yang <kever.yang@rock-chips.com>

arch/arm/dts/rk3399-firefly-u-boot.dtsi

@@ -5,3 +5,9 @@
 
 #include "rk3399-u-boot.dtsi"
 #include "rk3399-sdram-ddr3-1600.dtsi"
+
+/ {
+	chosen {
+		u-boot,spl-boot-order = "same-as-spl", &sdhci, &sdmmc;
+	};
+};

arch/arm/dts/rk3399-firefly.dts

@@ -14,7 +14,6 @@
 
 	chosen {
 		stdout-path = &uart2;
-		u-boot,spl-boot-order = "same-as-spl", &sdhci, &sdmmc;
 	};
 
 	backlight: backlight {