stm32mp: handle SYSRESET

Add support of sysreset with generic driver "syscon-reboot"
provided by RCC, for U-boot and for SPL.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/arch/arm/dts/stm32mp157-u-boot.dtsi b/arch/arm/dts/stm32mp157-u-boot.dtsi
index 7a9a4ce..1eca802 100644
--- a/arch/arm/dts/stm32mp157-u-boot.dtsi
+++ b/arch/arm/dts/stm32mp157-u-boot.dtsi
@@ -72,6 +72,10 @@
 	u-boot,dm-pre-reloc;
 };
 
+&rcc_reboot {
+	u-boot,dm-pre-reloc;
+};
+
 &pinctrl {
 	u-boot,dm-pre-reloc;
 };
diff --git a/arch/arm/dts/stm32mp157.dtsi b/arch/arm/dts/stm32mp157.dtsi
index 77953c8..b84899a 100644
--- a/arch/arm/dts/stm32mp157.dtsi
+++ b/arch/arm/dts/stm32mp157.dtsi
@@ -114,6 +114,13 @@
 				#reset-cells = <1>;
 				compatible = "st,stm32mp1-rcc-rst";
 			};
+
+			rcc_reboot: rcc-reboot@50000000 {
+				compatible = "syscon-reboot";
+				regmap = <&rcc>;
+				offset = <0x404>;
+				mask = <0x1>;
+			};
 		};
 
 		pinctrl: pin-controller {