stm32mp1: pwr: use the last binding for pwr

Update the driver to use the latest binding from kernel v5.5-rc1:
no more use syscon or regmap to access to pwr register and
only one pwr_regulators node with the compatibility "st,stm32mp1,pwr-reg"
is available.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
diff --git a/arch/arm/dts/stm32mp157a-dk1.dts b/arch/arm/dts/stm32mp157a-dk1.dts
index 4652253..dc61bfc 100644
--- a/arch/arm/dts/stm32mp157a-dk1.dts
+++ b/arch/arm/dts/stm32mp157a-dk1.dts
@@ -397,11 +397,9 @@
 	status = "okay";
 };
 
-&pwr {
-	pwr-regulators {
-		vdd-supply = <&vdd>;
-		vdd_3v3_usbfs-supply = <&vdd_usb>;
-	};
+&pwr_regulators {
+	vdd-supply = <&vdd>;
+	vdd_3v3_usbfs-supply = <&vdd_usb>;
 };
 
 &rng1 {