ARM: dts: stm32mp1: Add iwdg2 support for SPL

This patch adds independent watchdog support for stm32mp157c
in SPL.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
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 8102ce2..ba13ebb 100644
--- a/arch/arm/dts/stm32mp157-u-boot.dtsi
+++ b/arch/arm/dts/stm32mp157-u-boot.dtsi
@@ -106,6 +106,10 @@
 	u-boot,dm-pre-reloc;
 };
 
+&iwdg2 {
+	u-boot,dm-pre-reloc;
+};
+
 &pinctrl {
 	u-boot,dm-pre-reloc;
 };