arm: mvebu: add uartX labels for Armada SoC serial nodes

This patch adds uartX labels for Armada SoC serial nodes. This is
a preliminary work to be able to easily reference the serial lines
in Device Tree files. One expected use is when providing stdout-path
property for barebox.
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Link: https://lkml.kernel.org/r/0683d1a823fe9b75849f3dafcf1cf6ee291cdca6.1416613429.git.arno@natisbad.orgSigned-off-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/boot/dts/armada-370-xp.dtsi

@@ -151,7 +151,7 @@ i2c1: i2c@11100 {
 				status = "disabled";
 			};
 
-			serial@12000 {
+			uart0: serial@12000 {
 				compatible = "snps,dw-apb-uart";
 				reg = <0x12000 0x100>;
 				reg-shift = <2>;
@@ -160,7 +160,8 @@ serial@12000 {
 				clocks = <&coreclk 0>;
 				status = "disabled";
 			};
-			serial@12100 {
+
+			uart1: serial@12100 {
 				compatible = "snps,dw-apb-uart";
 				reg = <0x12100 0x100>;
 				reg-shift = <2>;

arch/arm/boot/dts/armada-xp.dtsi

@@ -53,7 +53,7 @@ i2c1: i2c@11100 {
 				reg = <0x11100 0x100>;
 			};
 
-			serial@12200 {
+			uart2: serial@12200 {
 				compatible = "snps,dw-apb-uart";
 				reg = <0x12200 0x100>;
 				reg-shift = <2>;
@@ -62,7 +62,8 @@ serial@12200 {
 				clocks = <&coreclk 0>;
 				status = "disabled";
 			};
-			serial@12300 {
+
+			uart3: serial@12300 {
 				compatible = "snps,dw-apb-uart";
 				reg = <0x12300 0x100>;
 				reg-shift = <2>;