ARM: DTS: stm32: add pwrcfg node for stm32f746

This node is needed to enable performance mode
when system frequency is set up to 200Mhz.
Signed-off-by: NPatrice Chotard <patrice.chotard@st.com>
Reviewed-by: NVikas Manocha <vikas.manocha@st.com>

arch/arm/dts/stm32f7-u-boot.dtsi

@@ -22,3 +22,7 @@
 		 u-boot,dm-pre-reloc;
 	};
 };
+
+&pwrcfg {
+	u-boot,dm-pre-reloc;
+};

arch/arm/dts/stm32f746.dtsi

@@ -99,12 +99,19 @@
 			status = "disabled";
 			u-boot,dm-pre-reloc;
 		};
+
+		pwrcfg: power-config@58024800 {
+			compatible = "syscon";
+			reg = <0x40007000 0x400>;
+		};
+
 		rcc: rcc@40023810 {
 			#reset-cells = <1>;
 			#clock-cells = <2>;
 			compatible = "st,stm32f42xx-rcc", "st,stm32-rcc";
 			reg = <0x40023800 0x400>;
 			clocks = <&clk_hse>;
+			st,syscfg = <&pwrcfg>;
 			u-boot,dm-pre-reloc;
 		};