stm32mp1: board: Update the way vdd-supply is retrieved from DT

Due to kernel DT alignment, pwr-supply is renamed to vdd-supply
and is a subnode of pwr-regulators.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/arch/arm/dts/stm32mp157a-dk1.dts b/arch/arm/dts/stm32mp157a-dk1.dts
index 1d5c1a6..ba612a5 100644
--- a/arch/arm/dts/stm32mp157a-dk1.dts
+++ b/arch/arm/dts/stm32mp157a-dk1.dts
@@ -308,7 +308,10 @@
 };
 
 &pwr {
-	pwr-supply = <&vdd>;
+	pwr-regulators {
+		vdd-supply = <&vdd>;
+		vdd_3v3_usbfs-supply = <&vdd_usb>;
+	};
 };
 
 &rng1 {