ARM: dts: mmp*: Fix serial port names

A preferred node name for serial ports is "serial":

  mmp2-olpc-xo-1-75.dt.yaml: uart@d4030000: $nodename:0: 'uart@d4030000'
      does not match '^serial(@[0-9a-f,]+)*$'
  ...
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200320174107.29406-6-lkundrak@v3.skSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/arm/boot/dts/mmp2.dtsi

@@ -208,7 +208,7 @@ timer0: timer@d4014000 {
 				clocks = <&soc_clocks MMP2_CLK_TIMER>;
 			};
 
-			uart1: uart@d4030000 {
+			uart1: serial@d4030000 {
 				compatible = "mrvl,mmp-uart";
 				reg = <0xd4030000 0x1000>;
 				interrupts = <27>;
@@ -218,7 +218,7 @@ uart1: uart@d4030000 {
 				status = "disabled";
 			};
 
-			uart2: uart@d4017000 {
+			uart2: serial@d4017000 {
 				compatible = "mrvl,mmp-uart";
 				reg = <0xd4017000 0x1000>;
 				interrupts = <28>;
@@ -228,7 +228,7 @@ uart2: uart@d4017000 {
 				status = "disabled";
 			};
 
-			uart3: uart@d4018000 {
+			uart3: serial@d4018000 {
 				compatible = "mrvl,mmp-uart";
 				reg = <0xd4018000 0x1000>;
 				interrupts = <24>;
@@ -238,7 +238,7 @@ uart3: uart@d4018000 {
 				status = "disabled";
 			};
 
-			uart4: uart@d4016000 {
+			uart4: serial@d4016000 {
 				compatible = "mrvl,mmp-uart";
 				reg = <0xd4016000 0x1000>;
 				interrupts = <46>;

arch/arm/boot/dts/mmp3.dtsi

@@ -318,7 +318,7 @@ timer: timer@d4014000 {
 				clocks = <&soc_clocks MMP2_CLK_TIMER>;
 			};
 
-			uart1: uart@d4030000 {
+			uart1: serial@d4030000 {
 				compatible = "mrvl,mmp-uart";
 				reg = <0xd4030000 0x1000>;
 				interrupts = <GIC_SPI 27 IRQ_TYPE_LEVEL_HIGH>;
@@ -328,7 +328,7 @@ uart1: uart@d4030000 {
 				status = "disabled";
 			};
 
-			uart2: uart@d4017000 {
+			uart2: serial@d4017000 {
 				compatible = "mrvl,mmp-uart";
 				reg = <0xd4017000 0x1000>;
 				interrupts = <GIC_SPI 28 IRQ_TYPE_LEVEL_HIGH>;
@@ -338,7 +338,7 @@ uart2: uart@d4017000 {
 				status = "disabled";
 			};
 
-			uart3: uart@d4018000 {
+			uart3: serial@d4018000 {
 				compatible = "mrvl,mmp-uart";
 				reg = <0xd4018000 0x1000>;
 				interrupts = <GIC_SPI 24 IRQ_TYPE_LEVEL_HIGH>;
@@ -348,7 +348,7 @@ uart3: uart@d4018000 {
 				status = "disabled";
 			};
 
-			uart4: uart@d4016000 {
+			uart4: serial@d4016000 {
 				compatible = "mrvl,mmp-uart";
 				reg = <0xd4016000 0x1000>;
 				interrupts = <GIC_SPI 46 IRQ_TYPE_LEVEL_HIGH>;