rockchip: phycore: remove no use "u-boot, boot0" in dts

We are using "u-boot,spl-boot-order" now and re-use the
definition from rk3288-u-boot.dtsi, so remove it directly here.

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

arch/arm/dts/rk3288-phycore-rdk.dts

@@ -55,11 +55,6 @@
 		stdout-path = &uart2;
 	};
 
-	config {
-		u-boot,dm-pre-reloc;
-		u-boot,boot0 = &emmc;
-	};
-
 	user_buttons: user-buttons {
 		compatible = "gpio-keys";
 		pinctrl-names = "default";