ARM: dts: stm32: Add clk-lse node's label on stm32f429

Add missing clk_lse label for node clk-lse.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32f429.dtsi

@@ -58,7 +58,7 @@
 			clock-frequency = <0>;
 		};
 
-		clk-lse {
+		clk_lse: clk-lse {
 			#clock-cells = <0>;
 			compatible = "fixed-clock";
 			clock-frequency = <32768>;