ARM: dts: stm32: fix a typo for DAC io-channel-cells on stm32f429

Fix a typo on STM32F429 DAC, e.g. s/channels/channel

Fixes: 25329b23 ("ARM: dts: stm32: Add DAC support on stm32f429")
Signed-off-by: NFabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: NAlexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32f429.dtsi

@@ -414,14 +414,14 @@
 
 			dac1: dac@1 {
 				compatible = "st,stm32-dac";
-				#io-channels-cells = <1>;
+				#io-channel-cells = <1>;
 				reg = <1>;
 				status = "disabled";
 			};
 
 			dac2: dac@2 {
 				compatible = "st,stm32-dac";
-				#io-channels-cells = <1>;
+				#io-channel-cells = <1>;
 				reg = <2>;
 				status = "disabled";
 			};