ARM: dts: dm814x: align UART node name with bindings

Bindings expect UART/serial node names to be "serial".

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Krzysztof Kozlowski <[e-mail]>

arch/arm/boot/dts/dm814x.dtsi

···
 				};
 			};
 
-			uart1: uart@20000 {
+			uart1: serial@20000 {
 				compatible = "ti,am3352-uart", "ti,omap3-uart";
 				ti,hwmods = "uart1";
 				reg = <0x20000 0x2000>;
···
 				dma-names = "tx", "rx";
 			};
 
-			uart2: uart@22000 {
+			uart2: serial@22000 {
 				compatible = "ti,am3352-uart", "ti,omap3-uart";
 				ti,hwmods = "uart2";
 				reg = <0x22000 0x2000>;
···
 				dma-names = "tx", "rx";
 			};
 
-			uart3: uart@24000 {
+			uart3: serial@24000 {
 				compatible = "ti,am3352-uart", "ti,omap3-uart";
 				ti,hwmods = "uart3";
 				reg = <0x24000 0x2000>;

arch/arm/boot/dts/dm816x.dtsi

···
 			ti,timer-pwm;
 		};
 
-		uart1: uart@48020000 {
+		uart1: serial@48020000 {
 			compatible = "ti,am3352-uart", "ti,omap3-uart";
 			ti,hwmods = "uart1";
 			reg = <0x48020000 0x2000>;
···
 			dma-names = "tx", "rx";
 		};
 
-		uart2: uart@48022000 {
+		uart2: serial@48022000 {
 			compatible = "ti,am3352-uart", "ti,omap3-uart";
 			ti,hwmods = "uart2";
 			reg = <0x48022000 0x2000>;
···
 			dma-names = "tx", "rx";
 		};
 
-		uart3: uart@48024000 {
+		uart3: serial@48024000 {
 			compatible = "ti,am3352-uart", "ti,omap3-uart";
 			ti,hwmods = "uart3";
 			reg = <0x48024000 0x2000>;