ARM: dts: Add USART1 pin config to STM32F429 boards

This patch selects USART1 pin configuration on PA9/PA10 pins
for both Eval and Disco boards.
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>

arch/arm/boot/dts/stm32429i-eval.dts

@@ -71,5 +71,7 @@ &clk_hse {
 };
 
 &usart1 {
+	pinctrl-0 = <&usart1_pins_a>;
+	pinctrl-names = "default";
 	status = "okay";
 };

arch/arm/boot/dts/stm32f429-disco.dts

@@ -71,5 +71,7 @@ &clk_hse {
 };
 
 &usart1 {
+	pinctrl-0 = <&usart1_pins_a>;
+	pinctrl-names = "default";
 	status = "okay";
 };

arch/arm/boot/dts/stm32f429.dtsi

@@ -263,6 +263,19 @@ gpiok: gpio@40022800 {
 				clocks = <&rcc 0 266>;
 				st,bank-name = "GPIOK";
 			};
+
+			usart1_pins_a: usart1@0 {
+				pins1 {
+					pinmux = <STM32F429_PA9_FUNC_USART1_TX>;
+					bias-disable;
+					drive-push-pull;
+					slew-rate = <0>;
+				};
+				pins2 {
+					pinmux = <STM32F429_PA10_FUNC_USART1_RX>;
+					bias-disable;
+				};
+			};
 		};
 
 		rcc: rcc@40023810 {