rockchip: Fix early use of bootph props

Running U-Boot on a ROCK 3 Model A result in the following:

  No serial driver found
  resetting ...
  no sysreset
  ### ERROR ### Please RESET the board ###

Replace bootph- props with u-boot,dm- props to fix this.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/dts/rk3568-rock-3a-u-boot.dtsi b/arch/arm/dts/rk3568-rock-3a-u-boot.dtsi
index ed47efa..b5ca23a 100644
--- a/arch/arm/dts/rk3568-rock-3a-u-boot.dtsi
+++ b/arch/arm/dts/rk3568-rock-3a-u-boot.dtsi
@@ -19,6 +19,6 @@
 
 &uart2 {
 	clock-frequency = <24000000>;
-	bootph-all;
+	u-boot,dm-pre-reloc;
 	status = "okay";
 };