ARM: dts: socfpga: rename gpio nodes

Since the Synopsys GPIO IP can support multiple ports of varying widths, it
would make more sense to have the GPIO node DTS entry as this:

gpio0: gpio@ff708000{
	porta{
	};
};

Also, this is documented in the snps-dwapb-gpio.txt.

Suggested-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>

arch/arm/boot/dts/socfpga.dtsi

@@ -547,15 +547,15 @@
 			status = "disabled";
 		};
 
-		gpio@ff708000 {
+		gpio0: gpio@ff708000 {
 			#address-cells = <1>;
 			#size-cells = <0>;
 			compatible = "snps,dw-apb-gpio";
 			reg = <0xff708000 0x1000>;
 			clocks = <&per_base_clk>;
 			status = "disabled";
 
-			gpio0: gpio-controller@0 {
+			porta: gpio-controller@0 {
 				compatible = "snps,dw-apb-gpio-port";
 				gpio-controller;
 				#gpio-cells = <2>;
@@ -567,15 +567,15 @@
 			};
 		};
 
-		gpio@ff709000 {
+		gpio1: gpio@ff709000 {
 			#address-cells = <1>;
 			#size-cells = <0>;
 			compatible = "snps,dw-apb-gpio";
 			reg = <0xff709000 0x1000>;
 			clocks = <&per_base_clk>;
 			status = "disabled";
 
-			gpio1: gpio-controller@0 {
+			portb: gpio-controller@0 {
 				compatible = "snps,dw-apb-gpio-port";
 				gpio-controller;
 				#gpio-cells = <2>;
@@ -587,15 +587,15 @@
 			};
 		};
 
-		gpio@ff70a000 {
+		gpio2: gpio@ff70a000 {
 			#address-cells = <1>;
 			#size-cells = <0>;
 			compatible = "snps,dw-apb-gpio";
 			reg = <0xff70a000 0x1000>;
 			clocks = <&per_base_clk>;
 			status = "disabled";
 
-			gpio2: gpio-controller@0 {
+			portc: gpio-controller@0 {
 				compatible = "snps,dw-apb-gpio-port";
 				gpio-controller;
 				#gpio-cells = <2>;