ARM: dts: stm32: add cortex-M4 pdds management in Cortex-M4 node

Add declarations related to the syscon pdds for deep sleep management.
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32mp151.dtsi

@@ -1124,6 +1124,11 @@ usb33: usb33 {
 			};
 		};
 
+		pwr_mcu: pwr_mcu@50001014 {
+			compatible = "syscon";
+			reg = <0x50001014 0x4>;
+		};
+
 		exti: interrupt-controller@5000d000 {
 			compatible = "st,stm32mp1-exti", "syscon";
 			interrupt-controller;
@@ -1705,6 +1710,7 @@ m4_rproc: m4@10000000 {
 			resets = <&rcc MCU_R>;
 			st,syscfg-holdboot = <&rcc 0x10C 0x1>;
 			st,syscfg-tz = <&rcc 0x000 0x1>;
+			st,syscfg-pdds = <&pwr_mcu 0x0 0x1>;
 			status = "disabled";
 		};
 	};