ARM: dts: stm32: enable RTC on stm32mp157c-ed1

Enable RTC (Real Time Clock) on stm32mp157c-ed1 board.
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32mp157c-ed1.dts

@@ -68,6 +68,10 @@ &i2c4 {
 	status = "okay";
 };
 
+&rtc {
+	status = "okay";
+};
+
 &uart4 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&uart4_pins_a>;