ARM: dts: stm32: enable RTC on stm32f469-disco

This patch enables RTC on stm32f469-disco with default LSE clock source.
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32f469-disco.dts

@@ -78,6 +78,10 @@ &clk_hse {
 	clock-frequency = <8000000>;
 };
 
+&rtc {
+	status = "okay";
+};
+
 &usart3 {
 	pinctrl-0 = <&usart3_pins_a>;
 	pinctrl-names = "default";