ARM: DT: STM32: add dma for usart1 on F429

Tested-by: NBruno Herrera <bruherrera@gmail.com>
Signed-off-by: NGerald Baeza <gerald.baeza@st.com>
Signed-off-by: NAlexandre TORGUE <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32f429.dtsi

@@ -162,6 +162,9 @@
 			interrupts = <37>;
 			clocks = <&rcc 0 164>;
 			status = "disabled";
+			dmas = <&dma2 2 4 0x400 0x0>,
+			       <&dma2 7 4 0x400 0x0>;
+			dma-names = "rx", "tx";
 		};
 
 		usart6: serial@40011400 {