ARM: tegra: Add serial port labels to Tegra124 DT

These labels will be used to provide deterministic numbering of consoles
in a later patch.
Signed-off-by: Lucas Stach <dev@lynxeye.de>
[treding@nvidia.com: drop aliases, reword commit message]
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra124.dtsi

@@ -286,7 +286,7 @@ pinmux: pinmux@0,70000868 {
 	 * the APB DMA based serial driver, the comptible is
 	 * "nvidia,tegra124-hsuart", "nvidia,tegra30-hsuart".
 	 */
-	serial@0,70006000 {
+	uarta: serial@0,70006000 {
 		compatible = "nvidia,tegra124-uart", "nvidia,tegra20-uart";
 		reg = <0x0 0x70006000 0x0 0x40>;
 		reg-shift = <2>;
@@ -299,7 +299,7 @@ serial@0,70006000 {
 		status = "disabled";
 	};
 
-	serial@0,70006040 {
+	uartb: serial@0,70006040 {
 		compatible = "nvidia,tegra124-uart", "nvidia,tegra20-uart";
 		reg = <0x0 0x70006040 0x0 0x40>;
 		reg-shift = <2>;
@@ -312,7 +312,7 @@ serial@0,70006040 {
 		status = "disabled";
 	};
 
-	serial@0,70006200 {
+	uartc: serial@0,70006200 {
 		compatible = "nvidia,tegra124-uart", "nvidia,tegra20-uart";
 		reg = <0x0 0x70006200 0x0 0x40>;
 		reg-shift = <2>;
@@ -325,7 +325,7 @@ serial@0,70006200 {
 		status = "disabled";
 	};
 
-	serial@0,70006300 {
+	uartd: serial@0,70006300 {
 		compatible = "nvidia,tegra124-uart", "nvidia,tegra20-uart";
 		reg = <0x0 0x70006300 0x0 0x40>;
 		reg-shift = <2>;