dm: dts: Convert driver model tags to use new schema

Now that Linux has accepted these tags, move the device tree files in
U-Boot over to use them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/dts/imx8mn-evk-u-boot.dtsi b/arch/arm/dts/imx8mn-evk-u-boot.dtsi
index 6c6c949..056ab31 100644
--- a/arch/arm/dts/imx8mn-evk-u-boot.dtsi
+++ b/arch/arm/dts/imx8mn-evk-u-boot.dtsi
@@ -6,21 +6,21 @@
 #include "imx8mn-ddr4-evk-u-boot.dtsi"
 
 &i2c1 {
-	u-boot,dm-spl;
+	bootph-pre-ram;
 };
 
 &{/soc@0/bus@30800000/i2c@30a20000/pmic@25} {
-	u-boot,dm-spl;
+	bootph-pre-ram;
 };
 
 &{/soc@0/bus@30800000/i2c@30a20000/pmic@25/regulators} {
-	u-boot,dm-spl;
+	bootph-pre-ram;
 };
 
 &pinctrl_i2c1 {
-	u-boot,dm-spl;
+	bootph-pre-ram;
 };
 
 &pinctrl_pmic {
-	u-boot,dm-spl;
+	bootph-pre-ram;
 };