ARM: dts: stm32: fix dma controller node name on stm32f746

Modify dma controller nodes name to fit with the standard naming.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32f746.dtsi

@@ -586,7 +586,7 @@ rcc: rcc@40023800 {
 			assigned-clock-rates = <1000000>;
 		};
 
-		dma1: dma@40026000 {
+		dma1: dma-controller@40026000 {
 			compatible = "st,stm32-dma";
 			reg = <0x40026000 0x400>;
 			interrupts = <11>,
@@ -602,7 +602,7 @@ dma1: dma@40026000 {
 			status = "disabled";
 		};
 
-		dma2: dma@40026400 {
+		dma2: dma-controller@40026400 {
 			compatible = "st,stm32-dma";
 			reg = <0x40026400 0x400>;
 			interrupts = <56>,