ARM: ux500: correct typo in pinctrl Device Tree node

The preference is to use '-' instead of '_' in compatible strings.
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/boot/dts/dbx5x0.dtsi

@@ -171,7 +171,7 @@ gpio8: gpio@a03fe000 {
 		};
 
 		pinctrl {
-			compatible = "stericsson,nmk_pinctrl";
+			compatible = "stericsson,nmk-pinctrl";
 			prcm = <&prcmu>;
 		};