ARM: dts: Ux500: move compatible string to chipset

Move the compatible string "stericsson,ab8500" from the board
definitions into the main node in the chipset file where it
belongs.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/boot/dts/ste-dbx5x0.dtsi

@@ -604,6 +604,7 @@ ab8500 {
 				#interrupt-cells = <2>;
 
 				ab8500_gpio: ab8500-gpio {
+					compatible = "stericsson,ab8500-gpio";
 					gpio-controller;
 					#gpio-cells = <2>;
 				};

arch/arm/boot/dts/ste-href.dtsi

@@ -223,7 +223,6 @@ msp3: msp@80125000 {
 		prcmu@80157000 {
 			ab8500 {
 				ab8500-gpio {
-					compatible = "stericsson,ab8500-gpio";
 				};
 
 				ab8500-regulators {

arch/arm/boot/dts/ste-snowball.dts

@@ -352,7 +352,6 @@ thermal@801573c0 {
 
 			ab8500 {
 				ab8500-gpio {
-					compatible = "stericsson,ab8500-gpio";
 				};
 
 				ext_regulators: ab8500-ext-regulators {